GIFT   OF 
MICHAEL  REESE 


DIOLOG* 

LIBRARY 

G 


EXPEKIMENTAL   MORPHOLOGY 


EXPERIMENTAL  MORPHOLOGY 


BY 


CHARLES  BENEDICT  DAVENPORT,  PH.D. 

INSTRUCTOR    IN    ZOOLOGY    IN    HARVARD    UNIVERSITY 


'      PART   FIRST  ' 

EFFECT  OF  CHEMICAL  AND ' PHYSICAL  AGENTS 
UPON  PROTOPLASM 


gork 
THE   MACMILLAN    COMPANY 

LONDON:  MACMILLAN  &  CO.,  LTD. 
1897 

AH  rights  reserved 


£S5 


COPYRIGHT,  1896, 
BY  THE  MACMILLAN  COMPANY. 


J.  S.  Cushing  &  Co.  —  Berwick  &  Smith 
Norwood  Mass.  U.S.A. 


SDelricatet) 

TO    THE   MEMORY    OF    THE    FIRST    AXD    MOST    IMPORTANT 
OF    MY    TEACHERS    IX    NATURAL    HISTORY 

MY   MOTHEK 


Die  morphologische  Betrachtung  setzt  also  eine  genaue 
chemisch  physikalische  Kenntniss,  1.  des  betreffenden 
Korpers  selbst,  und  2.  aller  der  bei  seiner  Entstehung  auf 
ihn  einwirkenden  Stoffe  und  Korper  voraus.  —  JAEGER, 
Zoologische  Brief e,  p.  9. 

La  vie  ne  se  co^oit  que  par  le  conflit  des  proprietes 
physico-chimiques  du  milieu  exterieur  et  des  proprietes 
vitales  de  1'organisme  reagissant  les  unes  sur  les  autres.  — 
BERNARD,  Rapport  sur  lea  progres  de  la  physiologic  generate 
en  France,  1867,  p.  5. 

There  can  be  little  doubt,  indeed,  that  every  science  as 
it  progresses  will  become  gradually  more  and  more  quan- 
titative. Numerical  precision  is  doubtless  the  very  soul  of 
science,  as  Herschel  says.  —  JEVONS,  Principles  of  Science, 
chap.  xiii. 


PEEFACE 

THE  problem  which,  since  the  time  of  Aristotle,  has  stood 
first  in  interest  and  importance  among  the  great  questions  of 
Biology  is  that  of  the  causes  which  direct  the  development  of 
the  individual  —  that  marvellous  process  by  which  the  germ 
is  built  up  into  the  complex  organism,  by  which  the  embryo 
clothes  itself  with  the  characters  peculiar  to  its  species,  by 
which  even  minute  individual  traits  of  form  and  action  are 
exactly  reproduced  in  the  offspring  from  its  parents. 

The  burden  of  clearing  up  this  problem  has  fallen,  naturally 
enough,  upon  the  shoulders  of  students  of  morphology.  For 
since  morphologists  deal  with  form,  they  are  properly  especially 
concerned  with  the  interpretation  of  form  —  they  may  well  be 
asked  to  account  for  it.  Thus  the  problem  of  development  is 
an  acknowledged  morphological  problem. 

Several  distinct  steps  can  be  recognized  in  the  progress 
which  has  been  made  in  the  interpretation  of  form.  The 
earlier  studies  were  concerned  chiefly  with  answering  the  ques- 
tion. What  are  the  differences  between  the  various  adult  forms  ? 
The  results  of  observations  and  reflections  relating  to  this 
question  constitute  the  sciences  of  descriptive  and  comparative 
anatomy.  Xext,  a  more  fundamental  inquiry  was  entered 
upon :  Sow  are  these  forms  produced  or  developed  ?  The 
results  of  observations  and  reflections  upon  this  subject  con- 
stitute the  science  of  comparative  embryology.  Finally,  in 
these  later  days  a  still  more  fundamental  question  has  come  to 
the  front :  Why  does  an  organism  develop  as  it  does  ?  What 
is  that  which  directs  the  path  of  its  differentiation?  This  is 
the  problem  which  the  new  school  of  "  Entwicklungsmecha- 
nik  "  has  set  for  itself  —  it  is  likewise  the  problem  with  which 
this  book  is  concerned. 


viii  PREFACE 

The  causes  which  determine  the  course  of  an  organism's 
development  are  numerous,  but  fall  into  two  general  categories  ; 
namely,  internal  causes,  which  include  the  qualities  of  the  devel- 
oping protoplasm ;  and  external  causes,  which  include  the 
chemical  and  physical  properties  of  the  environment  in  which 
the  protoplasm  is  developing.  The  internal  and  external  causes 
may  be  studied  separately,  and  in  order  to  disentangle  their 
effects  they  must  needs  be  studied  separately.  It  is  the  pur- 
pose of  the  present  work  to  consider  the  effects  resulting  from 
external  causes. 

When  we  wish  to  isolate  the  separate  effects  in  any  complex 
of  causes,  we  must  resort  to  the  well-known  procedure  of 
experimentation,  —  and  we  find,  indeed,  that  these  external 
causes  lend  themselves  readily  to  this  method  of  treatment. 
Accordingly  we  call  in  experiment  to  get  an  insight  into  the 
causes  of  organic  form,  and  thus  justify  the  name  which  we 
have  applied  to  our  study,  —  Experimental  Morphology. 

The  primary  subdivision  of  the  subject  is  based  upon  the 
morphogenic  processes  to  be  treated  of;  and  of  these,  four 
principal  classes  may  be  recognized.  The  first  includes  those 
processes  which  are  characteristic  of  all  living  protoplasm; 
the  second,  those  connected  with  growth ;  the  third,  those 
involved  in  cell-division;  and  the  fourth,  those  producing 
differentiation.  It  is  proposed  to  devote  one  part  of  the  work 
to  each  of  these  four  classes  of  processes. 

The  secondary  subdivision  may  be  based  upon  the  chemical 
and  physical  agents  whose  effects  we  wish  to  isolate.  These 
may  be  grouped  into  eight  categories,  determined  largely  by 
convenience  ;  namely,  1,  chemical  substances  ;  2,  water ;  3,  den- 
sity of  the  medium  ;  4,  molar  agents ;  5,  gravity  ;  6,  electri- 
city ;  7,  light ;  and  8,  heat.  It  is  proposed  to  devote  one 
chapter  to  a  consideration  of  the  effects  of  each  of  these  agents 
upon  protoplasm,  upon  growth,  upon  cell-division,  and  upon 
differentiation. 

Two  words  should  be  said  about  the  point  of  view  from 
which  this  book  has  been  written.  In  the  first  place,  the 
developing  organism  is  regarded  as  a  living  organism,  and  as 
such  endowed  with  irritability  and  capacity  of  response ;  con- 
sequently, at  the  outset,  we  must  especially  consider  the  phe- 


PREFACE  ix 

nomenon  of  response  to  external  stimuli.  Again  it  is  with 
living  organisms  that  we  have  to  deal,  and,  accordingly,  no 
distinction  should  be  made  between  animals  and  plants.  I 
have,  indeed,  made  no  such  distinction ;  nevertheless,  tastes 
and  training  have  led  me  to  lay  especial  stress  upon  animals. 
Even  this  is  unfortunate,  for  the  problem  with  which  we  are 
concerned  is  precisely  the  same  problem  in  all  living  organisms. 

In  the  second  place,  much  stress  is  laid  upon  the  quantitative 
measurement  of  agents  and  effects.  The  lack  of  precision  in 
many  investigations  can  hardly  be  too  strongly  decried  ;  for  it 
often  results  in  confusion  and  useless  disputes.  On  the  other 
hand,  there  is  good  reason  for  believing  that  exact  measure- 
ment is  the  key  to  many  of  the  most  puzzling  of  our  problems, 
and  important  results  are  to  be  expected  from  its  use. 

As  for  the  aim  of  the  book,  it  is  twofold.  I  have  hoped  on 
the  one  hand  that  it  might  be  readable  to  those  who  are  inter- 
ested in  the  general  matters  of  which  it  treats  —  matters  of 
importance  for  philosophy,  for  psychology,  and  for  pedagogy. 
For  man  is  an  organism,  and  the  development  of  his  qualities 
is  modified  by  just  those  agents  which  guide  the  development 
of  other  organisms.  My  primary  aim,  however,  has  been  a  dif- 
ferent one.  It  is  this  aim  to  which  other  purposes  have  been 
made  subservient,  which  justifies  the  historical  treatment  that 
has  been  often  adopted,  and  justifies  also  the  detailed  descrip- 
tions of  methods  which  the  lay  reader  will,  naturally,  omit. 
This  aim  is  so  to  exhibit  our  present  knowledge  in  the  field 
of  experimental  morphology  as  to  indicate  the  directions  for 
further  research. 

A  few  words  of  explanation  and  acknowledgment  are  neces- 
sary :  It  was  planned  at  the  first  to  issue  all  four  parts  of  the 
work  at  once  ;  but  the  task  grew  in  the  doing,  while  the  need 
of  its  publication  became  more  pressing.  So  it  was  decided 
to  issue  the  work  in  parts  as  soon  as  each  should  be  done. 
Even  under  this  arrangement  it  has  not  been  possible  to 
include  some  of  the  papers  of  the  last  six  months ;  especially 
I  regret  the  omission  of  important  papers  by  VERWORX  and 
LOEB  upon  Galvanotaxis.  In  writing  a  book  of  this  sort, 
which  draws  upon  several  sciences,  I  have  had  recourse  to  the 
kind  assistance  of  several  of  my  colleagues  in  the  physical  and 


x  PREFACE 

chemical  departments  of  the  University.  I  must  especially 
thank  for  favors  Professor  W.  C.  SABINE,  Dr.  G.  W. 
COGGESHALL,  and  Dr.  H.  E.  SAWYER.  Of  my  zoological 
associates,  I  am  greatly  indebted  to  Dr.  G.  H.  PARKER,  who 
has  read  nearly  the  entire  manuscript  and  has  offered  valuable 
criticisms  on  it,  and  to  Professor  E.  L.  MARK,  who  has 
read  parts  of  the  manuscript  and  proof  and  has  made  important 
suggestions  and  emendations.  I  am  also  greatly  indebted  to 
Mr.  CHARLES  BULLARD  for  his  kindness  in  making  photo- 
graphs of  figures  from  which  most  of  the  illustrations  of  the 
First  Part  were  reproduced.  Finally,  I  cannot  forbear  to  men- 
tion the  painstaking  work  of  my  wife,  GERTRUDE  GROTTY 
DAVENPORT,  in  preparing  the  manuscript  for  the  press  and 
revising  the  proofs. 

As  I  send  out  this  work  I  do  so  with  the  hope  that  it  may 
stimulate  to  even  greater  activity  in  the  field  of  experimental 
morphology.  The  subject  is  new,  its  importance  hardly  yet 
generally  recognized,  its  needs  incompletely  appreciated.  In 
its  scope  it  embraces  much  of  physics  and  chemistry,  for  life 
and  development  are  to  be  studied  as  the  physicist  studies  light 
and  heat,  or  as  the  chemist  studies  solutions  and  combustion. 
They  are  phenomena  which  must  be  analyzed  by  the  use  of 
instruments  of  precision  to  determine  the  quality  and  quantity 
of  the  acting  agents,  and  to  measure  the  change  in  the  phe- 
nomena resulting  from  a  change  in  these  agents.  No  other 
field  offers  a  better  opportunity  for  the  utilization  of  a  broad 
scientific  training.  The  times,  too,  are  auspicious.  Biology 
has  never  before  attracted  so  many  enthusiastic  workers  as  it 
does  to-day.  As  DRIESCH  has  said,  uDie  Lust  an  thatsach- 
licher  exacter  biologischer  Forschung  ist  erwacht";  and  the 
greatest  problem  of  morphology  is  ever  more  and  more  the 
object  of  this  biological  experimentation. 

CHARLES  BENEDICT  DAVENPORT. 
CAMBRIDGE,  MASS.,  Dec.  1, 1890. 


CONTENTS 


PAGE 

PREFACE •        .      vii 

CHAPTER  I 
ACTION  OF  CHEMICAL  AGENTS  UPON  PROTOPLASM 


§  1.   Modification  of  Vital  Actions 
1.   Oxygen           .... 

1 

2 

2.    Hydrogen 

5 

3.    Oxides  of  Carbon  .... 

6 

4.    Ammonia       ..... 

6 

5.    Catalytic  Poisons  .... 

7 

6.    Poisons  which  form  Salts 

12 

a.  Acids     

12 

b.  Soluble  Mineral  Bases   . 

13 

c.  Salts  of  Heavy  Metals    . 

13 

7.    Substitution  Poisons  •    . 

15 

8.    Sodic  Fluoride        .... 

21 

9.    Special  Poisons      .... 

22 

§  2.    Acclimatization  to  Chemical  Agents     . 

27 

§  3.    Chemotaxis  

32 

Summary  of  the  Chapter       .... 

45 

Appendix  to  Chapter  I           .... 

52 

Literature      

54 

CHAPTER  II 
EFFECT  OF  VARYING  MOISTURE  UPON  PROTOPLASM 

§  1.    On  the  Amount  of  AVater  in  Organisms 58 

§  2.   On  the  Effect  of  Desiccation  upon  the  Functions  of  Protoplasm    .  59 

1.  Effect  of  Dryness  on  Metabolism 59 

2.  Effect  of  Dryness  upon  the  Motion  of  Protoplasm          .         .  60 

3.  Desiccation-rigor  and  Death 60 

§  3.   On  the  Acclimatization  of  Organisms  to  Desiccation     ...  65 
§  4.    The  Determination  of  the  Direction  of  Movement  by  Moisture  — 

Hydrotaxis 66 

Literature ....  67 

XI 


xii  CONTENTS 

CHAPTER  III 
ACTION  OF  THE  DENSITY  OF  THE  MEDIUM  UPON  PROTOPLASM 

PAGE 

§  1.  Introductory  Remarks  upon  the  Structure  of  Protoplasm  and  the 

Physical  Action  of  Solutions  .......  70 

§  2.  Effect  of  Varying  Density  upon  the  Structure  and  General 

Functions  of  Protoplasm  .......  74 

§  3.  Acclimatization  to  Solutions  of  Greater  or  Less  Density  than  the 

Normal  .  .  .  .  .  .  .  .  .  .  .85 

§  4.    Control  of  the  Direction  of  Locomotion  by  Density  —  Tonotaxis  .       89 

Literature 93 

CHAPTER  IV 
ACTION  OF  MOLAR  AGENTS  UPON  PROTOPLASM 

§  1.   Effect  of  Molar  Agents  upon  Lifeless  Matter         ....  97 

§  2.  Effect  of  Molar  Agents  upon  the  Metabolism  and  Movement  of 

Protoplasm 98 

§  3.  Effect  of  Molar  Agents  in  Determining  the  Direction  of  Locomo- 
tion —  Thigmotaxis  (Stereotaxis)  and  Rheotaxis  .  .  .  105 

Literature 110 

CHAPTER  V 
EFFECT  OF  GRAVITY  UPON  PROTOPLASM 

§  1.    Methods  of  Study 112 

§  2.  Effect  of  Gravity  upon  the  Structure  of  Protoplasm  .  .  .113 
§  3.  Control  of  the  Direction  of  Locomotion  by  Gravity  —  Geotaxis  .  114 
Literature 124 

CHAPTER  VI 
EFFECT  OF  ELECTRICITY  UPON  PROTOPLASM 

§  1.    Concerning  Methods 126 

§  2.  The  Effect  of  Electricity  upon  the  Structure  and  General  Func- 
tions of  Protoplasm 129 

§  3.    Electrotaxis  ...........  140 

Summary  of  the  Chapter 151 

Literature 152 


CONTEXTS  xiii 


CHAPTER  VH 
ACTION  OF  LIGHT  UPON  PROTOPLASM 

PAGE 

§  1.    The  Application  and  Measurement  of  Light          ....  154 

§  2.   The  Chemical  Action  of  Light  upon  Xon-living  Substances          .  161 

1.  The  Synthetic  Effects  of  Light 162 

2.  Analytic  Effect  of  Light         ....  .  163 

3.  Substitution  Effects  of  Light 164 

4.  The  Isomerismic  and  Polymerismic  Changes  produced  by  Light  164 
§  3.    The  Effect  of  Light  upon  the  General  Functions  of  Organisms     .  166 

1.  Effect  of  Light  upon  Metabolism 166 

a.  The  Thermic  Effect  of  Light  on  Metabolism  .  .166 

b.  The  Chemical  Effect  of  Light  on  Metabolism  .  .     170 

2.  Vital  Limits  of  Light  Action  on  Protoplasm          .  .  .     171 

3.  Effect  of  Light  upon  the  Movement  of  Protoplasm  .  .     175 

a.  Effect  of  Low  Intensity  of  Light  on  Movement  —  Dark- 

rigor  ..........     175 

b.  Effect  of   High  Intensity  of   Light  on   Movement  — 

Light-rigor 178 

§4.    Control  of  the  Direction  of  Locomotion  by  Light  —  Phototaxis 

and  Photopathy *     .         .         .180 

1.  False  and  True  Phototaxis     .         .         .         .         .         .         .181 

2.  Distribution  of  Phototaxis  and  Photopathy  .         .  .     182 

a.  Protista .182 

b.  Cells  and  Cell-organs 189 

a.  Chlorophyll  Bodies 189 

(3.  The  Rearrangement  of  Pigment  in  Animal  Cells 

in  Response  to  Light  .....  192 
y.  The  Migration  of  Pigment  Cells  in  the  Metazoan 

Body .193 

c.  Metazoa 194 

3.  The  General  Laws  of  Phototaxis  and  Photopathy          .         .  196 

a.  The  Sense  of  the  Response     .         .         .         .         .         .196 

b.  The  Effective  Rays .201 

c.  Phototaxis  vs.  Photopathy     ......     203 

(L  The  Mechanics  of  Response  to  Light     ....     207 

Summary  of  the  Chapter .     210 

Literature  -1- 


xiv  CONTENTS 


CHAPTER 
ACTION  OF  HEAT  UPON  PROTOPLASM 

PAGE 

§  1.   Nature  of  Heat  and  the  General  Methods  of  its  Application          .  219 

§  2.   The  Effect  of  Heat  upon  the  General  Functions  of  Organisms      .  222 

1.  Effect  of  Heat  upon  Metabolism    ......  222 

2.  Effect  of  Heat  upon  the  Movement  of  Protoplasm  and  its 

Irritability          .........  225 

§  3.    Temperature-Limits  of  Life           .......  231 

1.  Temporary  Rigor  and  Death  at  the  Higher  Limit  of  Tem- 

perature, Maximum  and  Ultramaximum    .         .         .         .231 

2.  Temporary  Rigor  and  Death  at  the  Lower  Limit  of  Tempera- 

ture, Minimum  and  Ultraminimum    .....  239 

§  4.   Acclimatization  of  Organisms  to  Extreme  Temperatures      .         .  249 

1.  Acclimatization  to  Heat         .......  249 

2.  Acclimatization  to  Cold          .......  257 

§  5.   Determination  of  the  Direction  of  Locomotion  by  Heat  —  Ther- 

motaxis  .         .         .         .  '       .         .         .         .         .         .         .  258 

Notes  to  Table  XXI      ..........  263 

Literature      ...                  .  267 


CHAPTER  IX 

GENERAL  CONSIDERATIONS  ON  THE  EFFECTS  OF  CHEMICAL 
AND  PHYSICAL  AGENTS  UPON  PROTOPLASM 

§  1.    Conclusions  on  the  Structure  and  Composition  of  Protoplasm       .  274 

§  2.    The  Limiting  Conditions  of  Metabolism 275 

§  3.    The  Dependence  of  Protoplasmic  Movement  upon  Metabolism 

and  upon  External  Stimuli 277 

§  4.    The  Determination  of  the  Direction  of  Locomotion  278 


EXPERIMENTAL   MORPHOLOGY 

CHAPTER   I 

ACTION  OF  CHEMICAL  AGENTS   UPON  PROTOPLASM 

IN  this  chapter  it  is  proposed  to  consider  (I)  the  effect  of 
the  various  chemical  agents  upon  the  chemical  constitution  of 
protoplasm,  as  revealed  by  the  results  of  their  application, — 
death,  modification  of  the  metabolic  processes,  and  of  rate  of 
movement ;  (II)  the  phenomena  of  acclimatization  to  chemi- 
cal agents ;  and  (III)  the  effect  of  such  agents  in  determining 
the  direction  of  locomotion,  —  chemotaxis. 

§  1.    MODIFICATION  OF  VITAL  ACTIONS* 

The  vital  processes  are  chemical  processes,  taking  place  in  a 
highly  complex,  very  unstable,  constantly  changing  substance, 
whose  activities  we  call  life.  It  is  not  easy  to  study  this 
living  substance  chemically  by  the  ordinary  methods  ;  for 
these  usually,  first  of  all,  kill  the  substance.  That  the  living 
substance  and  the  dead  are  quite  different  is  illustrated,  for 
example,  in  the  action  of  diamid  (N2H2)  and  hydroxylamine 
(XH2  —  O  —  H),  which  show  no  action  upon  dead  protoplasm, 
but  are  powerful  poisons  for  all  living  plasm.  The  instability 
of  protoplasm  enables  us,  on  the  other  hand,  to  make  use  of 

*  In  the  preparation  of  this  section,  much  use  has  been  made  of  the  admirable 
work  of  LOEW  ('93).  Not  only  is  the  adopted  classification  of  poisons  for  the 
most  part  his,  but  also,  in  a  few  cases,  passages  from  his  book  have  been  translated 
in  toto  here.  Most  of  the  determinations  of  killing  strengths  of  the  various  re- 
agents for  which  no  other  authority  is  given  have  been  taken  from  LoEw'sbook. 

B  1 


2         CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

certain  indirect  means  for  determining  its  constitution.  Since 
death  is  due  to  chemical  change,  we  ought  to  determine  what 
substances  are  fatal  poisons  to  protoplasm  ;  and  since  every 
activity  of  protoplasm  is  a  chemical  process,  we  ought  to 
study  the  modifications  of  these  processes  by  the  action  of 
various  chemical  reagents. 

In  studying  the  behavior  of  protoplasm  in  the  presence 
of  various  reagents,  we  shall  make  use  especially  of  observa- 
tions upon  Protista,  sexual  cells,  and  tissue  cells.  In  cases 
where  sufficient  observations  on  isolated  plant  or  animal  cells 
are  wanting,  use  will  be  made  of  observations  upon  Metazoa.. 

At  the  outset,  attention  should  be  called  to  the  necessity 
of  a  more  quantitative  study  of  the  subject.  A  quantitative 
study  demands,  especially,  a  careful  noting  of  the  conditions 
of  the  experiment ;  for  the  various  physical  conditions  under 
which  the  reagent  is  applied  modify  the  result.  Thus,  it  has 
been  shown,  for  example,  by  RICHET  ('89,  p.  212)  that  with 
various  poisons  the  toxic  dose  diminishes  in  amount  with  the 
elevation  of  the  temperature  of  the  body. 

1.  Oxygen.  —  It  is  almost  certain  that  no  protoplasm  can 
long  survive  in  the  absence  of  oxygen.  Apparent  exceptions 
are  found  in  the  case  of  the  anaerobic  bacteria,  some  of  which 
are  killed  in  the  presence  of  free  oxygen,  but  multiply  rapidly 
when  the  oxygen  supply  is  cut  off.  It  has  been  suggested  that, 
in  the  case  of  these  and  some  other  parasitic  organisms,  oxygen 
is  derived  from  the  breaking  down  of  O -containing  compounds 
in  the  nutritive  medium.  (Cf.  LOEW,  '91,  p.  760.) 

The  effect  of  diminished  oxygen  upon  protoplasm  is  described 
by  CLARK  ('89,  pp.  370,  371)  and  by  DEMOOR  ('94,  p.  191). 
CLARK  determined  the  minimum  oxygen  pressure  necessary  for 
the  vital  movements  of  the  plasmodia  of  Myxomycetes  and  the 
protoplasm  of  plant  hairs  and  tissue  cells.  This  he  found  to 
range  from  1  mm.  (plasmodia  of  Myxomycetes)  to  3  mm.  (leaf 
hairs  of  Urtica)  of  mercury. 

DEMOOR*  subjected  Tradescantia  stamen  hairs,  in  water,  to  a 

*  In  studying  the  effect  of  a  vacuum,  DEMOOR  employed  a  piece  of  apparatus 
constructed  essentially  on  the  plan  of  an  ENGELMANN'S  chamber.  This  consists 
of  a  box  whose  top  is  a  centrally  perforated  metallic  diaphragm  and  whose 
bottom  is  a  circular  glass.  The  vertical  walls  consist  of  an  outer  cylinder,  at 


§  1]  MODIFICATIOX  OF  VITAL   ACTIONS  3 

pressure  of  6  to  8  cm.  of  Hg,  or  0.08  to  0.1  of  an  atmosphere 
(p.  71).  In  one  hour,  on  the  average,  the  protoplasmic  move- 
ments were  affected,  and  in  most  cells  ceased  in  2  to  3  hours, 
slight  oscillations  only  of  granules  occurring.  Thus,  not  death, 
but  arrest  of  activity,  occurred  during  this  period  as  a  result 
of  reduction  of  atmospheric  pressure  —  upon  which  the  amount 
of  oxygen  held  in  the  water  depends.  That  death  did  not 
occur  is  shown  by  the  fact  that  when  air  was  readmitted  at 
the  normal  pressure  the  protoplasm  promptly  regained  its  nor- 
mal activity.  Cells  immobilized  during  24  hours  regain  their 
movements  in  less  than  5  minutes,  and  these  become  normal  in 
from  10  to  20  minutes. 

Pure  oxygen  acts  in  an  opposite  fashion  from  diminished  oxy- 
gen tension,  exaggerating  the  activity  of  protoplasm.  Under 
its  action  the  protoplasmic  movements  are  much  accelerated, 
but  preserve,  meantime,  their  normal  character.  (Tradescantia 
hairs,  leucocytes;  DEMOOK,  '94,  pp.  192,  218.)  In  Ciliata  the 
rate  of  the  contractile  vesicle  does  not,  however,  seem  to  be 
altered.  (RossBACH,  '72,  p.  40.) 

Ozone  and  hydrogen  peroxide  produce  atomistic  "active"  oxy- 
gen by  becoming  split  up  in  the  plasma.  Ozone  (O3)  is  said 
to  kill  quickly  bacteria  in  water,  if  the  latter  does  not  contain 
too  much  organic  substance ;  in  the  dry  state,  however,  bacte- 
ria are  injured  only  slowly  by  it.  (OHLMULLEK,  '92,  p.  861.) 

Other  substances  which,  with  a  greater  or  less  degree  of 
probability,  may  be  said  to  act  through  oxidation  of  the  pro- 
toplasm, may  be  treated  of  here. 

Hydrogen  peroxide  (H2O2).  —  PAXETH  ('89)  added  one  part 
of  neutralized  H2O2  to  10,000  (0.01%)  of  hay  infusion,  and 
found  that  all  Ciliata  were  dead  within  15  to  30  minutes. 
Stronger  solutions  act  more  rapidly ;  and  even  in  a  0.005% 
solution,  only  part  of  the  animals  survived.  Algse  survived 
only  10  to  12  hours  in  a  completely  neutral  0.1%  solution. 
A  10%  solution  is  fatal  in  a  few  minutes.  (Cf.  BOKORNY, 
'86,  p.  355.) 

Salts  of  chromic,  manganic,  permanganic,   and   hypochlorous 

the  periphery  of  the  diaphragm,  and  an  inner  cylinder  at  the  inner  margin  of 
the  diaphragm.  An  inlet  and  an  outlet  tube  communicate  with  each  of  the 
spaces,  —  the  central  space  and  that  between  the  two  cylinders. 


4         CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

acids  act  as  intense  poisons,  apparently  by  directly  yielding 
oxygen  atoms  to  the  plasma  proteins. 

Sodic  chr ornate  (Na2CrO4). — Many  anaerobic  Schizophytes 
are  killed  even  by  a  0.05%  solution  of  this  salt.  Splenic  fever 
bacteria  do  not  develop  in  a  0.05%  solution  in  bouillon;  in 
an  agar-agar  solution,  they  do  not  cease  to  develop  until  a  con- 
centration of  0.5%  is  reached,  although  they  no  longer  produce 
spores  in  a  0.05%  solution.  Sodic  chromate  also  acts  strongly 
on  algae.  (LoEW,  '93,  p.  16.) 

Potassic  dichromate  (K2Cr2O7).  —  A  0.1%  solution  kills  algae 
(Spirogyra)  in  a  few  hours. 

Potassic  permanganate  (KMnO4)  is  an  energetic  poison  for 
algae  and  Infusoria.  A  0.2%  solution  kills  Infusoria  (Para- 
mecium)  in  one  minute. 

Chlorine,  bromine,  and  iodine,  as  well  as  hypochlorous  acid 
salts,  act,  even  in  very  considerable  dilution,  fatally  upon 
all  organisms,  by  splitting  water,  forming  hydro-halogen  com- 
pounds, and  leaving  the  oxygen  to  unite  with  the  living  proto- 
plasm. The  action  of  bromine  upon  glucose  may  be  written  — 

C6H1206  +  Br2  +  H20  =  C6H1207  +  2  HBr. 

glucose. 

(LoEW,  '93,  p.  15.) 

BINZ  has  pointed  out  that  (on  Infusoria)  the  poisonous 
action  of  these  three  halogens,  like  their  other  chemical  prop- 
erties, diminishes  with  increase  of  atomic  weight,  in  the  series 
Cl,  Br,  I.  (Compare  the  osmotic  effects  of  the  halogens,  p.  72.) 

Potassic  chlorate  (KC1O3)  —  also  similar  salts  of  I  and  Br  — 
oxidizes  in  an  essentially  different  fashion  from  the  permanga- 
nates. For  the  latter  oxidize  even  dead  organic  matter,  but 
the  former  does  not.  This  reagent  may  be  considered  a  pas- 
sively oxidizing  one.  Concerning  its  visible  effects,  we  find 
that  bacteria  in  general  are  injured  by  a  2%  solution;  with 
weaker  solutions  in  nutrient  media  the  bacteria  reduce  it  to 
KC1.  The  anaerobic  forms  are  affected  by  a  0.5%  solution; 
the  aerobic  withstand  up  to  3%.  Algae  (Spirogyra)  die  after 
a  few  days  in  a  0.01%  solution  of  the  salt.  (LoEW,  '93,  p.  17.) 

Arsenious  acid  (H3AsO3)  and  to  a  less  degree  arsenic  acid 
(H3AsO4)  are  poisons  which  BIKZ  and  SCHULZ  ('79)  believe 


§  1]  MODIFICATION  OF  VITAL   ACTIONS  5 

to  act  by  oxidizing  the  protoplasm.  Thus  H3AsO3  can  take 
up  free  oxygen  as  it  would  be  found  in  water,  and  it  can  part 
with  it  readily  to  the  protoplasm,  thus  oxidizing  and  eventually 
wholly  consuming  it.  Such  is  one  theory  of  its  action.  A  few 
words  as  to  effects  upon  Protista:  Infusoria  survive  in  0.1% 
potassic  arsenite  in  spring  water  only  a  short  time,  but  live 
for  weeks  in  a  0.1%  solution  of  the  potassic  arsenate.  (LoEW, 
'83,  p.  112.)  Algse  (Spirogyra)  are  killed  by  a  0.1%  solution 
of  potassic  arsenite  in  six  days,  —  the  protoplasm  contracts  and 
shows  formation  of  granules,  the  death  of  the  chlorophyll  bands 
preceding  that  of  the  cytoplasm.  The  same  solution  of  potassic 
arsenate,  meantime,  shows  no  injurious  action,  (LoEW,  '87, 
p.  445.)  Still  other  arsenious  acid  salts  tried  upon  other  algae 
(Zygnema,  Diatomacea),  upon  Infusoria,  and  upon  tadpoles 
showed  themselves,  uniformly,  more  powerful  agents  than  the 
corresponding  arsenic  salts.  The  lower  fungi  are  only  slightly 
affected  by  arsenious  salts ;  not  at  all  by  those  of  arsenic  acid. 

2.  Hydrogen.  —  KUHNE  ('64,  p.  52)  subjected  Amoeba  to  H 
for  24  minutes.  At  the  end  of  that  time,  some  individuals 
had  assumed  a  spherical  shape,  others  appeared  unchanged  in 
form,  but  were  motionless.  Similar  results  were  obtained  with 
Actinophrys,  the  plasmodium  stage  of  Myxomycetes,  and  with 
the  stamen  hairs  of  Tradescantia. 

DEMOOR  ('94,  p.  190)  also  experimented  upon  the  latter 
object,  and  his  results  are  worth  giving  in  detail.*  During 
the  first  moments  of  the  passage  of  the  gas,  the  protoplasmic 
movements  are  slightly  accelerated.  Soon  the  protoplasm  be- 
comes very  granular,  and,  after  a  variable  time,  15  to  40  minutes, 
is  quiet.  The  aspect  of  the  protoplasm  at  this  time  varies 
with  the  character  of  the  cell.  If  it  is  young,  having  a  large 
nucleus  and  without  a  primordial  utricle,  the  protoplasm  ap- 
pears uniformly  granular.  If,  on  the  contrary,  the  cell  possesses 
a  great  reserve  of  water,  with  long,  protoplasmic  filaments, 
the  protoplasmic  granules  become  more  refringent,  increase  in 
volume,  and  accumulate  around  the  nucleus,  —  the  peripheral 

*  Method :  The  hydrogen  gas  may  be  generated  in  a  KIPP'S  apparatus,  and 
should  pass  through  a  series  of  washing  flasks  containing,  e.g.,  solutions  of  potash 
and  acetate  of  lead.  See  VERWORX  :  Allgemeine  Physiol.,  p.  285.  DEMOOR 
kept  his  stamen  hairs  in  sugared  water  in  an  EXGELMAXN'S  chamber. 


6         CHEMICAL  AGENTS  AND  PROTOPLASM      [Cn.  I 

protoplasm  appearing  hyaline.  The  living  substance  is  in 
repose.  The  hydrogen  may  be  passed  through  the  apparatus 
containing  the  stamen  hairs  for  from  1  to  5  hours  without  any 
movement  or  other  change  appearing  in  the  protoplasm.  Air 
is  now  admitted.  The  protoplasmic  movements  rapidly  return  ; 
the  granules  at  first  oscillate  in  their  places,  then  gradually 
extend  the  range  of  their  movement.  In  5  to  6  minutes  the 
cell  has  regained  all  of  its  anatomical  and  physiological  charac- 
ters. A  similar  immobility  affects  also  leucocytes  subjected  to 
hydrogen.  This  occurs  in  about  an  hour;  but  there  is  great 
individual  variation  in  this  respect.  Upon  substituting  air, 
the  activity  of  the  protoplasm  is  resumed  in  from  10  to  20 
minutes.  Protoplasm  which  has  been  subjected  to  the  action 
of  hydrogen  thus  appears  not  to  be  permanently  modified,  since 
normal  movements  recur  rapidly  upon  readmitting  air.  It 
seems  probable,  therefore,  that  the  temporary  cessation  in  move- 
ments in  the  presence  of  hydrogen  is  due  to  the  exclusion  of 
oxygen  from  the  protoplasm. 

3.  The  two  Oxides  of  Carbon,  CO2  and  CO,  have  very  dif- 
ferent effects  upon  protoplasm.     Thus  DEMOOR  ('94,  pp.  191, 
202,  219)  found  that  whereas  the  former  immobilizes  quickly, 
but  kills  very  slowly,  perhaps  chiefly  by  asphyxia,  the  latter 
seems  in  some  cases  actively  to  attack  the  protoplasm.     In 
leucocytes,  the  ectosarc  is  separated  from  the  endosarc  in  a 
number  of  completely  hyaline  fragments  ;  the  endosarc  becomes 
vacuolated,  and  death  ensues  in  from  20  to  60  minutes.     Many 
bacteria  are  only  slightly  affected  by  CO. 

4.  Ammonia  (NH3).  —  A  10%   solution  provokes  vacuoli- 
J  zation,  partial  coagulation,  and   irregular  movements    in   the 
I  protoplasm  of  the  Tradescantia  hair.     The  cell  finally  enters 

into  repose,  all  the  granules  accumulating  around  the  nucleus. 
Washing  the  preparation  with  water  restores  the  original  char- 
acters of  the  protoplasm.  Thus,  ammonia  at  first  energetically 
excites  protoplasm,  later  producing  anaesthesia.  (DEMOOR,  '94, 
p.  193.)  Even  with  very  weak  aqueous  solutions  (0.005%), 
which  do  not  kill  the  protoplasm,  BOKORNY  ('88)  has  observed 
the  production  in  Spirogyra  cells  of  granules,  which  process 
does  not,  however,  seem  to  modify  the  normal  activities  of  the 
cell.  These  granules,  "  proteosomes,"  are  intensely  blackened 


§  1]  MODIFICATION  OF  VITAL   ACTIONS  7 

by  alkaline  (0.001%)  silver  solutions.     Other  basic  substances, 
like  potash  and  organic  amine  bases,  and  various   alkaloids, 
produce  the  same  effect.     (Cf.  LOEW  and  BOKORNY,  '89.) 
Azoimid.  —  LOEW  ('91)  has  studied  the  effect  upon  proto- 

NX 

plasm  of  this  somewhat  close  ally  of  ammonia,  ||    /NH.     The 

N' 

poisonous  action  of  this  substance  seems  to  depend  upon  its 
excessively  unstable  structure,  for  it  easily  disintegrates  with 
violent  explosion  and  production  of  ammonia.  This  latter 
then  produces  the  characteristic  granulations.  Infusoria  are 
killed  in  2  to  2J  hours  by  a  0.1%  solution  of  N3Na,  and  the 
water-living  Nematodes,  Planaria,  Ostracoda,  Copepoda,  and 
young  Planorbis  and  Lymnsea  are  killed  by  a  0.05%  solution  in 
30  to  40  minutes.  Algae  are  more  resistant. 

5.  Catalytic  Poisons.  —  There  is  a  large  number  of  unstable 
C-compounds  which  are  neither  acid  nor  basic  nor  characterized 
by  chemical  energy,  which  are,  nevertheless,  intense  poisons 
for  all  living  cells.  Here  belong  the  anaesthetics  —  ethylether, 
chloroform,  chloral,  carbontetrachlorid,  methylal,  alcohols,  car- 
bon disulphide,  etc.* 

NAGELI  believes  these  to  act  as  poisons  by  virtue  of  an  in- 
herent lively  condition  of  molepular  movement,  which  disturbs 
the  normal  condition  of  movement  in  the  living  plasma  body, 
and,  on  that  account,  produces  death.  LOEW  believes,  more 
precisely,  that  the  transmitted  condition  of  violent  movement 
leads  to  chemical  transformations  in  the  unstable  albumen  of 
the  protoplasm. 

As  examples  of  the  effect  of  the  mere  presence  of  many  un- 
stable carbohydrates  upon  chemical  processes,  it  has  been  found 
that  HC1  and  prussic  acid,  which  unite  alone  only  at  a  high 
temperature,  unite  in  the  presence  of  various  ethers  at  —15°. 
Again,  the  mere  presence  of  some  CH  compounds  transforms  a 
substance  into  its  isomeric  condition.  Thus,  thiourea  is  trans- 
formed by  an  alcoholic  solution  of  ainylnitrite  into  its  isomer 
rhodanammonium.  Such  poisons,  which  change  the  protoplasm 
by  transmission  of  molecular  movements,  may  be  called  cata- 

*  This  paragraph  and  the  two  following  are  largely  translated  from  LOEW 
('93). 


8         CHEMICAL  AGENTS  AXD  PROTOPLASM     [Cn.  I 

lytic  poisons ;  the  process  which  they  inaugurate  being  known 
as  catalysis  (apparently  produced  by  mere  contact). 

First  will  be  considered  the  laws  of  relation  between  molecular 
composition  and  strength  of  action.  We  may  begin  with  the 
me  than  series.  This  series,  which  has  CH3  —  as  its  base,  runs 

as  follows :  — 

CH4 
C2H6 
C3H8,  etc. 

In  the  members  of  this  series,  the  poisonous  action  increases 
up  to  a  certain  limit,  with  the  number  of  O  atoms ;  above  that 
limit  the  compounds  are  more  stable  and  are  more  indifferent ; 
e.g.  paraffine  (C21H44  to  C27H56). 

Beginning  with  methan,  CH4,  we  find  this  substance  —  marsh 
gas  —  innocuous  when  mingled  with  air.  As  the  If  atoms  become 
replaced  by  one  or  more  chlorine  atoms,  the  poisonous  qualities 
increase,  — 

CH3C1  is  slightly  anaesthetic, 

CHC13  =  chloroform, 

CC14  is  very  dangerous,  stupefying  involuntary  muscles. 

If  the  H  atoms  are  replaced  by  any  other  halogen,  —  e.g.  I,  — 
anaesthesia  is  produced  among  some  Vertebrates.  Thus,  0.5  to 
1  grain  of  CH2I2  kills  a  rabbit. 

In  ethan  (C2H6)  also,  when  Cl  replaces  H,  the  substance  be- 
comes a  more  active  poison ;  e.g.  C2H3C13,  methal  chloroform, 
acts  like  chloroform. 

Also,  among  the  sulphur  hydrocarbons  we  observe  the  same 
fact  of  increase  of  poisonous  action  with  increase  in  the  number 
of  Cl  atoms  to  the  molecule  ;  thus,  — 

sulphur  ethyl,  .  C2H5— S— C2H5  is  a  weak  poison, 

monochlorsulphurethyl,  C2H5— S— C2H4C1  is  a  stronger  poison, 
dichlorsulphurethyl,        C2H4C1  —  S  —  C2H4C1  is  a  very  powerful  poison. 

In  the  more  complex  sulphonic  hydrocarbons  of  the  methan 
series,  where  the  alkyls  CH3— ,  C2H5  — ,  etc.,  are  introduced, 
the  rule  holds  that  the  more  atoms  in  the  alkyl  the  more-  active 
the  substance  as  a  poison;  thus, — 


§  1]  MODIFICATION  OF   VITAL  ACTIONS  9 


/S02CH3 
/  C  \  is  not  poisonous  ; 

CH3/        \S02CH3 


v         /S02C2H5 
sulphonal  :  /  C  \  is  poisonous  ; 

CH/ 


/S02C2H5 

trional  :  /  C  \  is  poisonous  ;  and 

C2H/       \S02C2H5 

C2H5x         /S02C2H5 

tetronal  :  /  C  \  is  more  poisonous. 

C2H/     \S02C2H5 

The  same  holds  for  the  acetals  ;  thus,  — 

H\      /O.CH3  Hv         /O.C2H5 

>C  C  is  half  as  active  as  )  C  C 

H/       \O.CH3  CH3/        \O.C2H5 

We  find  the  same  thing  in  the  ethyl  group,  — 

CH3\  C2H5\ 

CH3—  C  -  OH  is  less  active  than  CH3—  C  -  OH. 

CH3/  CH3/ 

trimethalcarbinol.  ditnethalethylcarbinol. 

And  also  in  the  alcohols,  — 

methyl  alcohol,  CH3OH,  weak  action  ; 
ethyl  alcohol,  C2H5OH,  weak  action  ; 
isopropyl  alcohol,  C3H7OH,  stupefymg. 

A  few  words  now  concerning  the  morphological  changes  ob-' 
served  in  protoplasm  subjected  to  the  action  of  poisons  belonging 
to  this  group.     Here  belong  especially  the  various  anaesthetics. 

Chloroform  and  ether  seem  to  affect  all  protoplasm  anaes- 
thetically.  that  of  the  higher  plants  as  well  as  that  of  the 
higher  animals.  (BERNARD,  C.,  78,  and  ELFIXG,  F.,  '86.) 
KUHXE  (T>4,  p.  100)  first  studied  the  effect  of  chloroform  vapor 
upon  Tradescantia  hairs,  but  DEMOOR  ('94,  p.  193)  has  since 
described  the  action  of  this  reagent  in  much  more  detail. 
\  chloroform  water  at  first  (2  to  5  minutes)  produces  a  very 
intense  excitement  in  the  movements  of  the  protoplasm,  a 
strong  vacuolization  occurs,  and  then  the  cytoplasm  gradually 


10  CHEMICAL   AGENTS   AND  PROTOPLASM  [Cn.  I 

becomes  immobile  and  dies  in  from  15  to  30  minutes.  The 
nucleoplasm  is  less  energetically  acted  upon  than  the  cyto- 
plasm. Upon  swarm-spores,  which  are  highly  responsive  to 
light  (p.  182),  weak  solutions  of  ether  and  chloroform  have 
such  an  effect  that  without  preventing  locomotion  they  destroy 
the  power'  of  responding  to  the  stimulus  of  the  external  agent. 
So,  too,  the  migrations  of  the  chlorophyll  in  Metaphyta  *  under 
the  influence  of  light  (see  p.  189)  is  prevented.  Ciliata  are 
slightly  paralyzed,  for  the  period  of  the  contractile  vacuole  is 
diminished.  The  whole  cell  body  becomes  distended  with  water, 
and  the  trichocysts  are  exploded.  (SCHURMAYER,  '90,  p.  453.) 

When  chloroform  water  is  slowly  applied  to  leucocytes  they 
acquire  a  spherical  form  ;  when  quickly  applied  they  become 
immobile  without  change  of  form.  The  first  effect  is  a  very 
intense  increase  in  movements,  especially  of  the  ectosarc. 
Ultimate  washing  in  serum  suffices  to  restore  the  leucocyte 
to  its  wonted  activity ;  so  that  it  has  not  been  killed,  but  only 
ansesthetized.  (DEMOOR,  '94,  p.  217.) 

/OH 

Chloral  hydrate,  CC13  —  C  —  OH,  which  is  closely  related  to 

\H 
/Cl 

chloroform,  Cl  —  C  —  Cl,  acts  similarly  as  a  protoplasmic  anses- 

\H 

the  tic.  A  0.1%  solution  kills  Infusoria,  Rotifera,  and  diatoms 
in  24  hours,  but  filamentous  algse  and  Nematoda  withstand  it. 

Sulphonal  in  0.1%  solution  is  less  injurious  than  the  pre- 
ceding, since  during  24  hours  the  above-mentioned  organisms 
are  uninjured.  (Losw,  '93,  p.  25.) 

Upon  the  effect  of  alcohols  on  protoplasm,  extended  experi- 
ments have  recently  been  made  by  TSUKAMOTO  ('95).  These 
reveal  in  much  detail  the  peculiarities  of  action  of  the  different 
kinds.  I  give  three  tables  showing  the  time  of  resistance  in 
hours  of  various  organisms  to  the  various  alcohols,  constructed 
from  data  furnished  by  his  paper. 

*  ELFING,  F.  ('86,  pp.  47-51).  The  swarm-spores  employed  belonged  to  the 
species  Chlamydomonas  pulvisculus.  The  strengths  of  the  solutions  which 
inhibit  their  response  without  stopping  locomotion  are :  of  ether,  1%  to  5% ;  of 
chloroform,  12%  to  25%.  The  migration  of  chlorophyll  in  Mesocarpus  is  in- 
hibited by  a  1%  to  2%  ether  solution. 


§1] 


MODIFICATION  OF  VITAL   ACTIONS 


11 


TABLE   I 

TIME  (IN  HOURS)  OF  RESISTANCE  OP  TADPOLES  OP  BUFO  VULGARIS,  LAUR. 
(HIND  LEGS  HAD  JUST  APPEARED)  TO  VARIOUS  ALCOHOLS 


STRENGTHS. 

O.01% 

0.1% 

0.3% 

0.5% 

0.7% 

1.0% 

1.5% 

2.0% 

2.6% 

methylic*  .... 
ethylic  

4-5' 

1.0 

0.2-0.5 
1.5-2.0 

0.08 
0.15-0.25 

0.6 
0.5 

0.05-0.15 
0.15-0.33 

0.3 
0.2-0.3 

0.05-0.25 

0.15 
0.15 

stupor 

0.3-0.8 
0.16 

0.07-0.3 

propylic,  norm.  . 
propylic,  iso.  .  .  . 
butylic,  norm..  . 
butylic,  iso.  .  .  . 
butylic,  tertiary, 
amylic,  norm.  .  . 
allylic 

TABLE   II 

TIME  (IN  HOURS)  OF  RESISTANCE  OF  INFUSORIA  AND  OSTRACODA  TO  VARIOUS 

ALCOHOLS 


STRENGTHS. 

O.005% 

0.1% 

0.5% 

1.0% 

3.0% 

methvlic 

20 

ethylic  

4 

propylic,  norm  *.  . 

72  1 

propvlic  iso  

18 

butylic  norm 

48 

18 

butylic  iso    

72 

48t 

butylic  tertiary                                                      . 

48  +  t 

amylic  norm.  .  .  

24  + 

24 

allylic  

24 

*  The  structural  formulas  of  these  alcohols  are  given  here  for  reference :  — 

methylic H  -  CH2OH 

ethylic CH3  -  CH2OH 

propylic,  norm CH3  .  CH2  -  CH2OH 

propylic,  iso (CH3)2  -  CHOH 

butylic,  norm CH3  .  CH2  .  CH2  -  CH2OH 


butylic,  iso. 


CH3 
CH3 


>  CH  -  CH2OH 


butylic,  tertiary    .  ^3>COH-CH3 

L/.H.3 

amylic,  norm CH3  .  CH2  .  CH2  .  CH2  -  CH2OH 

allylic CH2.CH-CH2OH 

t  Ostracoda  only  ;  the  Infusoria  died  after  18  hours. 


OF  THF 

UNIVERSITY 


12 


CHEMICAL   AGENTS   AND  PROTOPLASM 


[Cn.  I 


TABLE   III 

TIME  (IN  HOURS)  OF  RESISTANCE  PERIOD  OF  SPIROGTRA  COMMUNIS  TO 
VARIOUS  ALCOHOLS 


STKENGTHS. 

0.005% 

0.01% 

0.05% 

0.1% 

0.5% 

1.0% 

2.0% 

3.0% 

4.0% 

methylic  
ethylic  

120 
72 

96 

72 

48 
48 

propylic,  norm.  . 
propylic,  iso.  .  .  . 
butylic,  norm.  .  . 
butylic,  iso.  .  .  . 
butylic,  tertiary, 
amylic,  norm.  .  . 
allylic  

66 

72 

24 

24 

72 
96 

24 

72 
48 
48 
48 
48 

i 

From  these  experiments  it  appears  that  allylic  alcohol  is  more 
injurious  than  the  others,  so  that  TSUKAMOTO  ('95,  p.  281) 
believes  it  to  attack  the  protoplasm  directly  rather  than  to  act 
merely  catalytically.  We  see  also  that  the  rule  enunciated 
above  about  the  greater  activity  of  substances  with  more  com- 
plex alkyls  holds  true  in  general.  Of  the  butylic  alcohols  the 
normal  is  the  most  poisonous ;  the  tertiary,  least. 

Carbonic  disulphide  (CS2)  is  one  of  the  more  powerful  cata- 
lytic poisons.  A  saturated  aqueous  solution,  which  contains 
only  a  trace  of  CS2,  nevertheless  kills  quickly  algse,  bacteria, 
and  the  lower  water  animals.  (LoEW,  '93,  p.  29.) 

6.  Poisons  which  form  Salts.  —  This  is  the  third  group  recog- 
nized by  LOEW.  In  this  case  we  have  to  do  with  acids  and 
bases  which  unite  with  the  protein  substances  of  the  pro- 
toplasm-producing salts.  Thus  disturbances  leading  to  death 
are  produced.  In  addition  this  group  comprises  the  poisonous 
metallic  salts.  So  we  may  recognize  three  groups:  a.  acids; 
b.  the  soluble  mineral  bases ;  c.  salts  of  heavy  metals. 

a.  Acids. — The  strong  inorganic  acids  act,  in  general,  more 
powerfully  than  the  organic.  Most  bacteria,  algae,  and  Infusoria 
are  very  sensitive  to  inorganic  acids  (see  MIGULA,  '90),  but 
splenic  fever  bacteria  resist  1%  HC1  for  24  hours,  and  their 
spores  2%  HC1  for  48  hours.  Mold  withstands  1%  phos- 
phoric acid.  Certain  tissues  have  gained  a  high  resistance 
capacity  to  inorganic  acids.  Thus,  the  gland  cells  of  marine 


§  1]  MODIFICATION  OF  VITAL  ACTIONS  13 

Gastropoda  (Dolium,  Cassis,  Tritonium,  Natica  heros)  secrete 
-2%  to  3%  H2SO4.     (LoEW.) 

To  organic  acids  many  algae  are  little  resistant.  Thus  Spiro- 
gyra  and  Sphseroplea  die  in  0.1%  malic  or  tartaric  acid  after 
30  minutes  ;  in  0.05%  malic  or  tartaric  acid  after  24  hours ;  in 
0.01%  of  these  same  acids  in  a  few  days.  Formic  acid  pre- 
vents development  of  bacteria  even  in  small  percents —  0.05% 
to  0.006%.  On  the  other  hand,  some  protoplasm  has  acquired 
a  resistance  to  organic  acids.  The  vinegar  eel  —  Rhabditis 
aceti  —  lives  in  4%  acetic  acid.  The  protoplasm  of  the  Dro- 
sera  tentacle  resists  0.23%  tartaric,  citric,  and  other  organic 
acids. 

b.  Soluble  mineral  bases,  including  those  of  corrosive  alkalies 
and  the  alkaline  earths  :  Ca,  Ba,  and  Sr.     The  corrosive  alka- 
lies cause  a  swelling  of  the  protoplasm,  but  the  primary  effect 
is  rather  a  chemical  one.     (Cf.  FROMAXX,  "84,  p.  90.) 

The  lower  water  animals  and  plants  are  quickly  killed  by 
0.1%  potassic  or  sodic  hydrate.  Thus,  the  movements  of 
Chara  cease  in  0.05%  KOH  in  35  minutes.  Bacteria  are  more 
resistant ;  the  limit  for  the  typhus  bacilli  being  between  0.10% 
and  0.14%,  and  for  the  cholera  bacillus,  between  0.14%  and 
0.18%.  Ascaris  is  still  more  resistant,  living  for  20  minutes 
in  a  2%  solution  of  XaOH. 

CaO  is  still  more  powerful.  A  0.007%  to  0.025%  solution 
in  bouillon  kills  bacilli.  A  0.013%  solution  is  fatal  to  alga3 
like  Spirogyra. 

K2CO3  kills  bacteria  in  0.8%  to  1.0%  solutions. 

Xa2CO3  kills  Ascaris  in  a  5.8%  solution  after  5  to  6  hours. 
(LoEW,  '93,  pp.  33,  34.)  FROMAXX  has  discussed  the  histo- 
logical  changes  in  protoplasm  after  treatment  in  Na2CO3. 

It  is  difficult  to  say  whether  the  action  of  some  of  these  re- 
agents may  not  be  an  osmotic,  rather  than  a  chemical  one. 
The  action  of  Xa2CO3,  for  example,  as  described  by  FROMAXX, 
is  very  similar  to  that  of  NaCl,  whose  action  is  probably  solely 
osmotic. 

c.  Salts  of  Heavy  Metals. — The  method  of  action  of  these 
poisons  has  been  accounted  for  upon  the  following  grounds: 
When  amido-acids  (which  are  found  as  disintegration  products 
of  all  animal  tissues)  are  treated  Avith  salts  of  the lieavy  metals, 


14        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

the  hydrogen  in  either  the  carboxyl-group  or  the  amido- 
group  can  be  replaced  by  the  metal.  Likewise  the  hydrogen 
of  the  amido-group  in  urea  derivatives  and  many  bases  are 
replaceable  by  metals.  In  the  still  more  complicated  protein 
stuffs  the  H  bound  to  the  N  or  O  can  be  replaced.  Many 
metals,  indeed,  like  silver  or  mercury  replace  preferably  the  H 
of  the  amido-groups,  and  on  this  account,  perhaps,  their  salts 
are  especially  poisonous.  (LoEW,  '93,  p.  34.) 

Salts  of  Hg,  Ag,  and  Cu  cause  death  to  Spirogyra  even  in 
a  dilution  of  1  :  1,000,000 ;  the  chlorophyll  bodies  being  first 
affected.*  Upon  the  bacteria  of  splenic  fever  the  double 
cyanides  of  Ag,  Hg,  and  Au  are  the  most  injurious,  next  those 
of  Cu,  Pb,'  and  Zn,  and,  finally,  those,  of  Pt,  Ir,  and  Os.  Tad- 
poles and  Tubifex  are  killed  in  24  hours  by  solutions  of  CuSO4 
weaker  than  0.00005%.  (LOCKE,  '95,  p.  327.)  Among  mer- 
curic salts,  splenic  fever  bacteria  do  not  develop  in  0.0003% 
HgCl2  in  nutritive  bouillon,  nor  0.0125%  in  blood.  Lactic  acid 
bacteria  do  not  reproduce  in  0.0007%.  Mold  spores  are  killed  in 

*  In  this  connection  reference  must  be  made  to  the  posthumous  paper  of 
NAGELI  ('93),  "  Ueber  oligodynamische  Erscheinungen  in  lebenden  Zellen." 
This  author  found  that  water  distilled  in  copper  vessels  or  1  litre  of  water  in 
which  12  clean  copper  coins  had  stood  for  four  days  acted  fatally  upon  Spiro- 
gyra. The  water  was  found  in  one  such  case  to  contain  1  part  Cu  in  77,000,000  of 
water.  It  was  believed  to  be  in  solution  in  the  form  of  the  hydroxyd  (CuH2O2). 
Similarly  produced  solutions  of  other  metals,  Ag,  Zn,  Fe,  Pb,  Hg,  had  a  simi- 
larly fatal  effect  upon  Spirogyra.  NAGELI  believed  that  the  effect  of  the  metals 
was  not  a  chemical  one,  but  was  due  to  a  new  force  —  "  oligodynainic."  Besides 
the  fact  of  the  action  of  very  dilute  solutions,  the  only  evidence  he  adduced  for 
the  new  force  was  based  on  the  difference  of  action  on  the  chlorophyl  bands  of 
solutions  of  1 : 1000  or  1 : 10,000  and  1 : 10,000,000.  In  the  weaker  solutions 
("  oligodynamic  "  action)  the  bands  alone  were  drawn  away  from  the  cell- wall, 
in  the  stronger  solution  (chemical  action)  the  whole  peripheral  protoplasm  was 
shrunken  away.  It  does  not  seem  necessary  to  invoke  a  new  force  to  explain 
the  action  of  weak  solutions:  first,  because  the  two  actions  are  not  sharply 
separated,  according  to  NAGELI'S  own  data;  secondly,  because  the  chlorophyll 
bands  are  in  general  more  sensitive  than  the  rest  of  the  protoplasm  (p.  5)  ; 
and,  thirdly,  because  the  action  of  so  weak  a  solution  is  not  surprising  in  view  of 
the  fact  that  Spirogyra  is  one  of  the  least  resistant  of  organisms.  Even  in  a 
comparatively  resistant  organism,  like  Stentor,  a  solution  of  1 :  80,000,000  HgCl2 
produces  acclimatization  to  the  poison  and  1 : 10,000,000  has  an  injurious  effect. 
Yet  between  the  action  of  such  solutions  and  those  of  1 : 1000  there  is  a  complete 
graduation  in  increasing  effect.  (Seep.  30.)  Even  in  NAGELI'S  experiments- 
solutions  of  less  than  1 : 100,000,000  had  little  action. 


§  1]  MODIFICATION   OF   VITAL   ACTIONS  15 

0.1%.  NEAL  and  I  have  found  that  Stentor  cceruleus  is  killed 
by  a  0.001%  solution  HgCl2  in  a  few  seconds.  (Cf.  p.  30.) 
Ascarids  die  in  a  0.1%  solution  in  an  hour.  (SCHRODER,  '85.) 

Silver  salts  occasionally  act  upon  bacteria  more  energetically 
that  those  of  Hg.  Cadmium  and  zinc  salts  are  poisonous  —  the 
former  more  so  than  the  latter.  Thus,  whereas  0.015%  of  cad- 
mium sulphate  inhibits  reproduction  of  lactic  acid  bacteria, 
0.1%  of  zinc  sulphate  is  not  injurious.  Many  salts  of  thallium 
are  likewise  active.  Thus  LOEW  ('93,  p.  37)  found  that  in 
0.1%  thallium  sulphate  Spirogyra  died  in  4  to  6  hours. 

7.  Substitution  Poisons.  —  In  this  group  LOEW  places  cer- 
tain nitrogenous  substances  which  attack  the  ainido  and  alde- 
hyde groups  of  living  protoplasm.  These  are  extremely  unstable 
substances  and  may  therefore  be  transformed  by  agents  which 
have  no  effect  upon  dead  protoplasm.  The  supposed  method 
of  action  of  a  poison  upon  an  aldehyde  may  be  illustrated  in 
the  case  of  the  poison  hydroxylamine  (H2N  —  OH);  which 
justifies  at  the  same  time  the  term  "substitution  poisons." 


,0  ^N 

+  H>0. 


-  2-  - 

\H  \H 

any  aldehyde.  hydroxylamine.  an  aldoxim. 

Hydroxylamine.  —  This  is  a  general  and  powerful  poison. 
Thus,  among  the  lower  organisms,  a  solution  of  neutral  hy- 
droxylamine of  — 

0.001%  kills  diatoms  within  24  hours.     (LOEW,  '85a,  p.  523.) 
0.005%  kills  in  36  hours  Infusoria  which  withstand  a  similar  con- 

centration of  strychnine.     (LOEW.) 
0.01%     kills  diatoms  in  something  less  than  15  hours;  Planaria  and 

leeches  in  12  to  16  hours.     (LOEW.) 
0.1%       paralyzes  the  muscles  of  Rotifera  in  10  to  15  minutes  ;  those 

of  Xais  in  20  to  30  minutes.     (HOFER,  '90,  pp.  324,  325.) 
0.2%       kills  Rotifers,  Copepoda,  and  Isopods  in  1  hour  (LOEW)  ; 

stupefies  Yorticella  in  from  2  to  10  minutes.     (HOFER, 

'90,  p.  325.) 
0.25%     stupefies  Stentor  in  10  to  20  minutes.     (HOFER.) 

Benzenylamidoxim  and  acetoxim,  more  complex  derivatives  of 
hydroxylamine,  are  somewhat  less  poisonous. 


16        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

Diamid,  or  hydrazin  (H2N  —  NH2)  in  the  form  of  neutral 
solutions  of  the  sulphate  is  a  rapid  poison.     A  solution  of  - 

0.01%     kills  various  alga  species  in  1  to  2  days. 

0.02%     is  injurious  to  bacteria. 

0.05%     kills  various  water  animals  within  12  hours.     (LOEW,  '93.) 


Phenylhydrazin  , 

H  f 
solution  of  — 


N-NH, 


is  more   powerful.      A 


0.0067%  kills  Infusoria  and  algae  within  18  hours. 

0.05%       prevents  the  development  of  bacteria  and  mucors. 

As  free  ammonia  (NH3)  is  a  far  weaker  poison  than  diamid 
(H2N  —  NH2),  so  anilin  (C6H5NH2)  is  far  weaker  than  phenyl- 
hydrazin  (C6H5  .  NH  .  NH2). 

Passing  now  to  the  more  complex  nitrogenous  compounds, 
we  find,  first,  that  bodies  which  possess  slight  or  no  poisonous 
power,  and  contain  tertiary  N,  can  become  strong  poisons  by 
addition  of  H  and  formation  of  imido-groups  (i.e.  groups  which 
can  be  derived  from  ammonia  by  the  substitution  for  two  H 
atoms  of  bivalent  acid  radicals) ;  thus,  — 

/CH  =  CH\  /CH2  -  CH2\ 

CH/  )K  CH/  O 

^CH  -  CH^  \CH2  -  CH/ 

pyridin  (weaker  poison).  piperidin  (stronger  poison) 

/HC  =  HC\  /H,C  -  H,C\ 

"  >N  CH/  ) 

C^  \CH9  -  CH/ 

I  I 

CH  CH2 

/     \  I 

3  CH3  CH2 

coUidin  (weak). 

CH3 

coniin  (violent). 

In  the  preceding  and  the  two  following  cases  it  is  seen  that, 
in  general,  when  there  is  a  hydrogen  atom  of  the  amid  radical 
(NH2)  unreplaced  by  an  alkyl,  the  substance  is  poisonous. 


§  1]  MODIFICATION  OF   VITAL   ACTIONS  17 

ONLY  SLIGHTLY  POISONOUS.  VIOLENT  POISONS. 


)CH  -  C6H5  I  /CH 

6H5-CH  =  N/  C6H5-C     =     W 


-  C6H5 

hydrobenzamid.  amarin. 


/CH  =  CH\  CH  =  CH\ 

CH/  I  >H 

CH  =  CHX 


pyridin.  pyrrol.* 

This  increased  poisonousness,  correlated  with  the  presence 
of  H  joined  to  N,  may  be  accounted  for  by  the  union  of 
this  H  with  the  O  of  the  ketons  or  aldehydes  of  the  living 
substance. 

Likewise  when  one  or  more  H  atoms  of  the  amido-group 
are  replaced  by  an  acid  radical  (e.g.  that  of  acetic  acid, 
CO  .  CH3),  the  poisonous  qualities  of  the  substance  are  con- 
siderably diminished  ;  thus,  — 

MORE  POISONOUS.  LESS  POISONOUS. 

C6H5NH2  CeHsNH  .  CO  -  CH3 

anilin.  antifebrin.t 


.  NH2  C6H5ira  .  NH  .  CO  .  CH3 

phenylhydrazin.  pyrodin. 


/NH« 

HN  =  C(  HN  =  C( 


.C0.^xx2 

guanidin.  dicyandiamidin. 

In  like  manner  when,  in  an  imido-group,  the  H  (of  the  NH 
radical)  is  replaced  by  alkyls  (e.g.  CH3),  the  substances  become 
less  poisonous  ;  thus,  — 

*  While  a  0.07  %  solution  of  pyrrol  kills  Isopods,  Rotifers,  Planaria,  etc.,  in 
about  1  hour,  these  organisms  withstand  a  solution  of  pyridin  of  the  same 
strength.  (LoE\v,  '87,  p.  444.) 

t  SCHURMAYER  ('90,  p.  445)  finds  that  upon  Ciliata  (Carchesium)  a  0.1% 
solution  slightly  accelerates  at  first  the  action  of  the  cilia,  diminishes  the  rate  of 
succession  of  the  phases  of  the  contractile  vacuole,  and  leaves  the  protoplasm 
permanently  more  or  less  paralyzed, 
c 


18  CHEMICAL   AGENTS  AXD  PROTOPLASM  [Cn.  ] 

NH-CH  N.CH3-CH 

I  II  I  II 

CO       C  -  KH  CO  C  -  N  .  CH3 

I  I  ^>CO  I  I  \CO 

NH-C=NX  NH  C  =  N  ' 

xanthin.  theobromine. 

N.CH3-CH 
I  II 

CO  C-N.CH, 

I  I  ^CO 

N  .  CH3  -  C  =  N  ' 

coffein. 

are  successively  less  poisonous.     (LoEW,  '93,  p.  46.) 

H 
I 

HV      /Cv      /a 
\c/     \c/ 

While  benzol          \  \          is  rather  inactive,  8  grammes 

/C\       /Gv 
H/      \C/     ^H 

I 

H 

per  day  being  withstood  by  the  human  organism,  with  the 
replacement  of  the  H  atoms  by  OH  the  substance  becomes 
more  poisonous  in  direct  proportion  to  the  number  of  H 
atoms  thus  replaced.  (LoEW,  '87,  p.  440.)  Thus  there  fol- 
low in  order  of  poisonousness  :  — 

H  H  H 

I  I  I 

HC/    \C-OH      HC/    \0-OH      HO-C/    \C-OH 

II  II  II 

HC  \        /CH  HC  >. 


I  I  I 

H  OH  OH 

phenol  (monoxybenzole).  resorcin  (dioxybenzole).  phloroglucin  (trioxybenzole). 

Phenol  (or  carbolic  acid)  and  its  derivatives  attack  unstable 
substances,  especially  aldehydes,  forming  insoluble  products. 

Phenol  itself  produces  in  the  higher  animals  a  paralysis  of 
the  nerve  centres.  Algae  die  in  a  1%  solution  after  20  to  30 


§  1]  MODIFICATION  OF  VITAL  ACTIONS  19 

minutes;  in  a  0.1%  solution  after  3  days.  Infusoria  die 
quickly  in  a  1%  solution.  Ascaris  lives  only  3  hours  in  a 
0.5%  solution. 

Resorcin  (0.5  g.)  is  hypnotic  to  man;  0.085  g.  per  kg.  is 
fatal  to  dogs.  Its  isomer  —  pyrocatechin  —  is  more  active. 
0.1%  of  it  in  spring  water  kills  diatoms  and  Infusoria  after 
a  few  minutes,  and  filamentous  algae  in  a  few  hours;  while, 
with  resorcin,  Infusoria,  diatoms,  and  green  algae  live  several 
hours  —  even  as  long  as  18  hours. 

By  replacing  one  of  the  H  atoms  of  phenol  by  CO  OH  (or 
carboxyl),  thus  producing  salicylic  acid,  the  poisonous  qualities 
are  reduced. 

Hydrocyanic  Acid,  CNH.  —  The  action  of  this  substance  is 
peculiar  in  that,  acting  on  the  central  nervous  system,  it  is 
in  small  quantities  a  more  violent  poison  for  Vertebrates  than 
for  Invertebrates.  Hydrocyanic  acid  acts  upon  aldehydes  — 
in  dilute  solutions  upon  the  most  unstable  compounds  only  ;  in 
stronger  concentration  upon  all  aldehydes.  Its  peculiar  work- 
ing may  be  hypothetically  explained  by  assuming  the  aldehydes 
of  the  ganglion  cells  to  be  more  unstable  than  those  of  other 
cells,  so  that  traces  of  CNH  which  do  not  injure  other  cells 
destroy  quickly  the  nerve  cells.  (LoEW.) 

The  action  may  be  shown  by  the  equation,  — 


E\  K\ 

)C  =  0  +  CNH  =       )C—  OH. 
H/  H/ 

aldehyde. 

The  degree  and  variety  of  its  action  may  be  inferred  from 
the  following  data,  taken  from  LOEW  ('93):  Infusoria  die 
quickly  in  a  0.1%  solution,  but  Ascaris  resists  a  3%  solution 
for  75  minutes.  The  resistance  of  the  hedgehog  to  CNH  is 
remarkable  ;  five  times  the  dose  which  killed,  in  4  minutes,  a 
cat  weighing  2  kg.  produced  in  the  hedgehog  only  a  slight 
sickness.  A  myriapod  (Fontaria)  excretes  CNH  when  irri- 
tated. Certain  salts  of  CNH  act  as  poisons  ;  e.g.  (CN)2Hg, 
Na2Fe(CN)5NO. 

Hydric  sulphide  acts  as  a  poison  either  by  deoxidizing  the 

plasma, 

H2S  +  0  =  H20  4-  S, 


20  CHEMICAL  AGENTS  AND  PROTOPLASM  [Cn.  I 

or  by  acting  on  the  aldehydes, 

E\  Bv 

)C  =  O  +  H2S  =       )C  =  S  +  H20. 
H/  H/ 

It  acts  rather  energetically  upon  algse  and  Infusoria.  In  Ver- 
tebrates, the  central  nervous  system  is  attacked  and  the  oxy- 
hsemoglobin  of  the  blood  is  altered. 

Sulphurous  oxide  (SO2)  attacks  members  of   the   aldehyde 


c  =  o  +  SOSKH  =     ;c—  OH 

H/  H/    \H 

aldehyde. 

0.1%  kills  lower  fungi  in  a  few  minutes,  0.01%  in  a  few  hours. 
Selenous  oxide  (SeO2),  which  acts  chemically  much  like  SO2 
and  has  a  much  greater  molecular  weight  (64  :  111),  acts  less 
energetically  as  a  poison.  A  0.1%  solution  kills  Spirogyra 
and  Zygnema  in  3  hours,  while  0.01%  is  scarcely  injurious. 
Tellurous  oxide  (TeO2,  mol.  wt.  =  157)  is  non-poisonous, 
although  chemically  closely  allied  to  the  two  preceding. 

(BOKORNY,   '93.) 

Aldehydes.  —  The  poisonous  action  of  these  substances  de- 
rived from  oxidation  of  alcohol  is  dependent  upon  their  insta- 
bility. So  we  find  that  an  aldehyde,  which,  like  grape  sugar, 
is  fairly  stable,  is  likewise  non-poisonous  ;  while  formaldehyde, 
which  is  very  unstable  and  active,  is  correspondingly  poisonous. 
Aldehydes  attack  especially  the  unstable  amides,  affording  ni- 
trogenous compounds  ;  e.g.  — 

C6H5  •  NH2  +  CH20  =  C6H5NCH2  +  H2O. 

Now,  even  in  passive  albumens,  part  of  the  N  is  in  the  form 
of  amido-groups  ;  for,  in  treating  with  nitric  acid,  much  nitro- 
gen is  set  free,  which  would  not  occur  were  all  of  the  N  second- 
arily or  tertiarily  bound  up.  (LoEW,  '93,  p.  58.)  Hence  the 
poisonousness  of  aldehydes  for  living  albumens. 

Formaldehyde.  —  This  substance  (H  —  CH  :  O)  acts  upon 
propeptones  and  upon  albumen,  affording  compounds  which  are 
not  readily  soluble.  An  aqueous  solution  of  — 


§  1]  MODIFICATION   OF  VITAL  ACTIONS  21 


0 


0.01  %  is  fatal  to  bacteria. 
.05%  kills  worms,  molluscs,  and  isopods  in  2  hours.     (LOEW,  '88, 

p.  40.) 
1.00%  kills  Spirogyra  very  quickly.     (CoHN,  '94,  p.  5.) 


A  weak  solution  seems  to  act  anaesthetically  upon  Noctiluca. 

(MASSART,  '93,  p.  65.) 

When  various  radicals  are  substituted  in  H  —  CH  :  O,  the 
substance  acts  more  like  a  catalytic  poison.  Thus,  ethyl- 
aldehyde  (CH3  —  CHO)  is  anaesthetic  ;  and  paraldehyde 
(CH3-CHO)3  kills  algae  in  a  solution  of  0.002%  in  24 
hours  and  causes  protoplasm  to  become  immobile  either  (leuco- 
cytes) after  momentary  stimulation  (DEMOOR,  '94,  p.  218)  or 
(Xoctiluca)  at  once  (M  ASSART,  '93,  p.  66). 

Several  derivatives  of  ethylaldehyde  are  poisonous.  LOEW 
('93,  p.  60)  has  shown  that  in  a  0.1%  solution  of  the  neutral 
sulphate  of  NH2  —  CH2  —  CH  :  (OC2H5)2,  amidoacetal,  Infu- 
soria, and  diatoms  die  within  15  hours,  and,  somewhat  later, 
filamentous  algae. 

Nitrous  acid,  as  is  well  known,  produces,  even  in  great  dilu- 
tion, OH-cornpounds  from  amido-compounds  (R  —  NH2)  ;  or 
else,  under  certain  conditions,  especially  with  aromatic  amido- 
compounds,  diazo-compounds  result  ;  e.g.  — 


C2H5  .  NH2  +  HO  .  NO  =  C2H5  .  OH  +  NT,  +  H2O, 

amine.  alcohol. 

and 

C6H5  .  XH2  .  HN03  4-  HO  .  NO  —  C6H5  .  N2ON02  +  2  H2O. 

aniline  nitrate.  diazobenzene  nitrate. 

Thus  a  solution  of  0.001%  of  free  nitrous  acid  is  poisonous 
to  algae,  and  more  so  than  nitric  acid.  The  lower  fungi  are 
also  very  sensitive  to  nitrous  acid.  Its  action  as  an  acid  is 
weak,  so  that  its  salts  are  set  free  in  the  presence  of  even  the 
weaker  organic  acids.  On  this  account,  even  neutral  nitrates 
kill  such  plants  (some  algae,  e.g.  Spirogyra)  as  have  an  acid 
cell-sap. 

8.  Sodic  Fluoride.  —  The  poisonous  action  of  the  fluorides 
of  the  light  metals,  and  especially  sodium,  has  not  hitherto 
been  explained.  A  0.2%  solution  of  NaF  kills  various  algae 
(Oscillaria,  Cladophora,  CEdogonium,  diatoms)  within  24  hours, 


22        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

producing  a  change  in  size  of  the  nucleus.     (LoEW,  '92.)     A 
1%  solution  kills  the  nerves  of  a  frog  in  2  hours. 

9.  Special  Poisons.  —  Toxic  Protein  Compounds.  Little  need 
be  said  here  concerning  the  recent  discoveries  of  poisonous 
albuminoids  excreted  by  disease-producing  bacteria,  or  of  those 
secreted  by  the  parasitized  body  (alexines) .  Similar  compounds, 
highly  poisonous  to  Vertebrates,  have  been  extracted  from  the 
seeds  of  some  Phanerogams,  e.g.  ricin,  from  the  seeds  of  Rici- 
nus  communis  (castor-oil  bean);  abrin,  from  the  seeds  of  the 
leguminous  Abrus  precatorius,  L. ;  and  phallin,  from  the  toad- 
stool Agaricus  phalloides,  Fr.  Finally,  in  this  group  may  be 
placed  a  large  number  of  protein  substances  derived  from 
animals,  which  are  more  or  less  poisonous  to  a  greater  or 
smaller  number  of  kinds  of  protoplasm.  The  poison  of  the 
rattlesnake  (Crotalus)  and  of  the  cobra  (Naja)  is  fatal  to 
Vertebrates  in  small,  hypodermically  injected,  doses.  Hydra, 
Turbellaria,  Rotifera,  and  Crustacea  are  also  affected  by  it ; 
but  Infusoria  and  Flagellata  are  apparently  unaffected.  (HEi- 

DENSCHILD,  '86,  p.  330.) 

It  is  important  that,  according  to  the  experiments  of  several 
investigators,  among  the  earlier  of  whom  may  be  mentioned 
DAREMBERG  ('91)  and  BTJCHNER  ('92),  the  various  species  of 
Vertebrates  possess  protein  substances  in  their  blood  serum 
which  are  to  a  certain  extent  injurious  to  other  species,  since 
the  blood  serum  of  any  one  species  will  destroy  the  red  and 
white  blood  corpuscles  of  another.  The  poisonous  action  of 
these  animal  protein  substances  seems  to  be  due  to  their  un- 
stable character,  whereby  they  easily  form  unions  with  the 
unstable  groups  of  the  protoplasm,  frequently  producing 
thereby  violent  poisons  which  work  as  substitution  poisons. 
(LoEW,  '93,  pp.  81-84.) 

Alkaloids.  —  These  basic,  nitrogenous  compounds  have,  for 
the  most  part,  very  complex  molecules,  so  that  their  structure 
has,  in  many  cases,  not  been  determined.  Consequently  the 
nature  of  their  chemical  action  upon  protoplasm  is,  in  general, 
unknown. 

LOEW  suggests  ('93,  p.  85)  the  following  theory  of  action  of 
alkaloids.  The  bases  unite  with  the  active  protein  substances 
of  the  cell,  and  thereby  introduce  a  disturbance  of  equilibrium 


§  1]  MODIFICATION  OF  VITAL   ACTIONS  23 

in  the  plasma  body  —  a  disturbance  which  is  especially  mani- 
fest in  their  action  upon  the  protoplasm  of  ganglion  cells.  The 
capacity  of  this  union  is  influenced  by  various  factors  :  by 
the  configuration  and  degree  of  dilution  of  the  poison ;  by  the 
degree  of  instability  of  the  kind  of  protoplasm  acted  upon ; 
by  the  configuration  of  the  molecule  of  the  active  protein 
substance  in  the  cells ;  and  by  the  specific  (micellar)  structure 
of  the  plasma  body.  That  organic  bases  can  unite  with  active 
albumen  is  known  from  observations  upon  plant  cells  contain- 
ing stored-up  active  protein  substances.  If  the  configuration 
of  the  albumen  molecule  and  the  general  texture  of  the  pro- 
toplasm favor  the  attack  by  the  base,  a  disturbance  of  the 
equilibrium  of  the  protoplasm  will  result,  even  in  considerable 
dilution  of  the  poison. 

The  alkaloids  affect  chiefly  the  nervous  tissue  in  the  higher 
animals,  producing,  in  some  cases,  paralysis ;  in  others,  increased 
activity.  Thus,  curarin  is  paralytic  in  its  action,  while  the 
closely  allied  strychnin  is  (in  dilute  solutions)  stimulating 
upon  nerve  cells.  Since  action  is  almost  confined  to  nerve 
tissue,  additional  evidence  is  afforded  of  the  extraordinary 
instability  of  the  nervous  protoplasm. 

The  dissimilar  effect  of  an  alkaloid  upon  the  different  sub- 
stances constituting  nerve  protoplasm  gives  an  idea  of  the 
complexity  of  the  latter.  Thus,  an  alkaloid  may  stimulate 
nerves  with  certain  functions  to  increased  activity,  and  may 
reduce  nerves  in  the  same  body,  having  other  functions,  to 
depression  and  paralysis;  e.g.  nicotin  excites  sensory  nerves, 
and  depresses  the  activity  of  the  cardio-motor  nerves. 

It  is  important  that  many  of  these  alkaloids  act  also  upon 
Protozoa  and  the  lowest  plants,  in  which  nervous  substance  is 
still  undifferentiated.  Other  of  these  alkaloids,  however,  do 
not  act  upon  Protista. 

We  will  now  proceed  to  an  examination  of  the  action  of  the 
principal  vegetable  alkaloids,  arranged  according  to  the  sys- 
tematic position  of  the  plants  from  which  they  are  obtained. 

Nicotin.  —  The  effect  produced  by  nicotin  is  directly  pro- 
portional to  the  differentiation  of  nervous  substance ;  thus,  it 
is  almost  inoperative  on  Protozoa  and  Actinia.  Hydra  is  not 
very  sensitive,  0.5%  being  a  fatal  dose.  A  solution  of  0.05% 


24  CHEMICAL  AGENTS  AND   PROTOPLASM  [Cn.  I 

causes  Medusae  to  become  quiet  in  30  minutes,  and  is  fatal  to 
the  earthworm  in  a  few  hours  ;  Echinoderms  are  paralyzed  by 
a  0.05%  solution  in  30  minutes  ;  Palsemon  (after  temporary 
stimulation)  is  paralyzed  by  a  0.01%  solution  in  30  minutes  ; 
Sepiola  is  killed  by  0.005%  in  less  than  a  minute.  (GREEN- 
WOOD, '90.) 

Veratrin,  Atropin,  and  Cocaine  act  upon  Vertebrates  so  as 
to  excite  the  central  nervous  system  at  first,  and  then  to 
paralyze  it.  All  act,  however,  as  poisons  upon  undifferenti- 
ated  protoplasm  (Protozoa).  Thus,  ROSSBACH  ('72)  found 
that  when  Ciliata  were  subjected  to  veratrin  chloride  and 
to  atropin  sulphate,  a  peculiar  rotary  movement  took  place 
about  one  end  as  a  fixed  axis.  Then  imbibition  of  water 
with  great  vacuolation  of  the  protoplasm  occurred.  Later, 
the  contractile  vacuole  fails  to  contract,  and  protoplasmic 
movements  cease  a  few  seconds  after.  (Cf.  KUHNE,  '64, 
pp.  47,  65,  100.) 

Cocaine  is  apparently  a  benzol  derivative,  closely  related, 
chemically,  to  atropin.  Its  formula  is  thus  given:  — 


CH 


H2C      CH2      CH 

CO.C6H5. 


C  -  COO  .  CH 


Its  action  upon  Protista  has  been  studied  by  CHAKPENTIER 
('85),  ADDUCO  ('90),  SCHURMAYER  ('90,  pp.  438-448),  AL- 
BERTONI  ('91,  p.  318),  DANILEWSKI  ('92),  and  MASSART 
('93,  p.  66);  upon  sexual  cells,  by  O.  and  R.  HERTWIG  ('87, 
p.  159)  and  ALBERTONI  ('91,  p.  309);  and  upon  tissue  cells 
by  ALBERTONI.  The  result  has  been  to  show  that  cocaine 
first  stimulates  for  a  very  short  time  to  excessive  activity,  and 
then  stupefies  and  paralyzes.  With  the  paralysis,  a  strong 
vacuolation  of  the  protoplasm  occurs,  since  the  excretory  func- 
tion of  the  contractile  vacuole  is  inhibited  (SCHURMAYER,  '90, 
p.  439).  Cocaine  acts  similarly  upon  the  nerve  centres  and 
muscles  of  the  more  differentiated  animals. 


11  j 

i  :; 


§  1]  MODIFICATION  OF  VITAL  ACTIONS  25 

Morphin  acts  less  violently  upon  the  nervous  tissue  of  Ver- 
tebrates. It  has  a  very  weak  action  upon  Protista. 

Strychnin,  chemically  considered,  is  an  alkaloid  with  the 
formula:  C21H22X2O2 ;  specific  gravity,  1.359  at  18°;  soluble 
to  about  0.025%  in  water  at  14.5°;  has  a  very  bitter  taste. 
The  nitrate  is  generally  employed.  The  action  of  strychnin 
upon  Protista  is  known  through  the  studies  of  MAX  SCHULTZE 
('63,  p.  32),  BINZ  ('67,  pp.  384-389),  ROSSBACH  (72,  pp. 
52-54),  and  SCHURMAYER  ('90,  pp..  423-433).  KRUKEXBERG 
('80)  has  studied  its  effects  upon  higher  Invertebrates.  Its 
action  upon  sexual  cells  has  been  studied  by  the  brothers 
HEBTWIG  ('87,  pp.  153-156,  164). 

Although  not  fatal  to  bacteria  and  only  in  strong  solutions 
fatal  to  the  large  fungi,  strychnin  is  a  nearly  universal  proto- 
plasmic poison.  It  kills  the  protoplasm  of  the  Drosera  ten- 
tacles and  hinders  the  development  of  peas,  corn,  and  lupines. 
The  amount  of  strychnin  that  Protozoa  can  withstand  has  been 
variously  stated,  while  all  authors  admit  considerable  individ- 
ual variation  in  this  respect.  Probably  Protozoa  cannot  ordi- 
narily resist  a  saturated  solution  for  one  minute.  ROSSBACH 
(72,  p.  52)  found  that  no  infusorian  of  his  cultures  survived 
a  "0.1%  solution"  long  enough  to  be  placed  under  the  mi- 
croscope. A  0.02%  or  0.01%  solution  can  be  withstood  for 
a  few  minutes  (0.01%  solution  was  withstood  for  5  minutes, 
SCHURMAYER).  As  for  the  weakest  solution  that  will  kill, 
SCHURMAYER  found  that  a  Paramecium  resisted  for  only  15 
to  20  minutes  so  weak  a  solution  as  0.0005%,  while  ROSSBACH 
found  Stylonychia  little  affected  by  a  0.0055%  solution.  The 
spermatozoa  of  Echinoids,  according  to  the  HERTWIGS  ('87, 
p.  164),  so  resist  a  0.01%  solution  that  after  180  minutes  the 
movement  is  only  somewhat  retarded.  Echinoid  eggs  are  in- 
jured in  a  few  minutes  by  0.005%. 

The  injurious  action  of  strychnin  on  Protozoa  varies  in  the 
different  groups,  the  resistance  capacity  increasing,  in  general, 
with  the  height  of  systematic  position  of  the  group.  The 
first  effect  in  Ciliata  is  an  increased  activity  of  the  cilia;  if 
irri  are  present,  these  strike  more  powerfully;  locomotion  is 
abnormally  rapid ;  but  the  movements  lack  coordination,  and 
a  rotation  takes  place  about  the  axis  of  progression.  Next, 


26        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

the  movements  become  so  disorganized  that  locomotion  is  im- 
possible, despite  accelerated  cilia-motion.  Finally,  the  move- 
ments suddenly  cease,  death  intervening.  (SCHURMAYER,  '90, 
pp.  423-426.)  The  process  of  excretion  seems  to  be  especially 
affected.  Immediately  after  the  addition  of  a  0.02%  solution, 
the  contractile  vesicle  increases  to  from  4  to  10  times  its  normal 
diameter,  and  loses  its  spheroidal  form.  In  a  slightly  greater 
dilution,  0.014%,  the  contractile  vesicle  momentarily  constricts, 
but  in  diastole  gains  twice  its  normal  diameter,  and  the  time 
between  phases  of  contraction  is  greatly  increased.  Thus,  the 
normal  rate  of  contraction  for  Euplotes  at  15°  C.  is  between 
30  and  35  seconds ;  but  in  a  0.014%  solution  of  strychnin 
this  is  diminished  to  1  in  500  seconds.  Frequently,  several 
vacuoles  are  formed,  and,  eventually,  the  whole  body  becomes 
greatly  vacuolated,  and  death  intervenes.  (RossBACH,  '72, 
pp.  52,  53.)  Many  higher  organisms  are  not  very  sensitive 
to  strychnin.  Thus,  Ascaridse  have  a  considerable  resistance, 
which  SCHRODER  ('85,  p.  307)  ascribes  to  their  not  opening 
their  mouths  in  the  solution,  the  poison  being  thus  obliged 
to  pass  through  the  skin.  So,  too,  snails  were  found  by 
KRTJKENBERG  ('80,  p.  100)  to  be  very  resistant  to  strychnin. 

Curare,  or  urare,  is  an  alkaloid,  derived  from  Strichnos 
species.  The  commercial  substance  is  very  variable  in  com- 
position. NIKOLSKI  and  DOGIEL  ('90)  have  studied  the  effects 
of  this  drug  upon  various  organisms.  Upon  adding  a  few 
drops  of  a  0.8%  solution  of  curare  to  water  containing  an 
amoeba,  the  first  effect  is  a  shrinking  towards  a  spherical  form 
and  a  cessation  of  all  movements.  Subsequent  washing  in 
water  ultimately  restores  the  normal  movements.  As  is  well 
known,  it  paralyzes  also  the  protoplasm  of  the  nerve  endings. 

Quinine,  or  chinin  (C20H24N2O2). — The  "sulphate,"  which 
is  first  produced  in  the  process  of  extraction,  is  commonly 
employed.  This  is,  moreover,  more  soluble  than  the  pure 
alkaloid,  1  part  dissolving  at  9.5°  in  788  parts  of  water.  In- 
vestigations on  the  action  of  this  poison  upon  protoplasm  have 
been  made  especially  by  BINZ  in  a  series  of  papers  beginning 
with  '67;  by  ROSSBACH  ('72)  on  Protozoa;  by  TEN  BOSCH 
('80)  on  leucocytes;  by  O.  and  R.  HERTWIG  ('87)  on  sexual 
cells;  and  by  KRUKENBERG  ('80)  on  higher  Invertebrata. 


TJN- 


§  2]  ACCLIMATIZATION  TO   CHEMICAL  AGENTS 

Amoeba,  Actinophrys,  and  various  Infusoria  are  killed  by  a 
0.1%  solution  in  a  few  minutes,  and  leucocytes  and  eggs  of 
Echinoicls  are  paralyzed  even  by  a  0.005%  solution.  Its  action 
is  thus  more  powerful  than  that  of  strychnin.  The  proto- 
plasm at  first  contracts,  then  gradually  dissolves  and  streams 
away.  Upon  the  higher  animals,  quinine  so  acts  as  to  paralyze 
the  central  nervous  tissue  (in  Mollusca,  KRUKENBERG,  '80, 
p.  10),  and  it  affects  the  cerebrum  and  heart  ganglia  of 
mammals. 

Antipyrin,  or  phenyldimethylpyrazolon,  is  an  alkaloid  de- 
rived from  and  belonging  clearly  to  the  benzol  type,,  in  which 
one  atom  of  H  is  replaced  by  a  complex  atom-group,  as  may  be 
seen  from  the  formula  — 

.pTT  TTP r*      r'Ti 

/\jjn.\.  ±1  \J  \j   VyXlg 

HCX         ^ULC  |  | 

I                 I                OC\      /N-CHS 
HCv  ,G ^NX 


The  effect  of  this  agent  upon  Protozoa  has  been  studied  by 
SCHTTRMAYER  ('90,  pp.  434-437)  and  M ASSART  ('93,  p.  64). 
A  solution  of  0.1%  acting  for  80  minutes,  caused  Oxytricha 
at  first  to  move  more  rapidly,  but  eventually  to  become 
transformed  into  a  shapeless  mass,  whose  protoplasm  disinte- 
grates. Acting  upon  Noctiluca,  a  0.25%  solution  causes  a 
bright  glimmer  immediately  after  applying,  followed  by  dark- 
ness again.  Thus  there  is  here  a  momentary  hyperesthesia. 


§  2.   ACCLIMATIZATION  TO  CHEMICAL  AGENTS 

It  is  clear  that  the  protoplasm  of  different  organisms  is  dis- 
similar. We  see  this  in  the  different  reactions  to  the  same 
chemical  agent.  Not  only  is  the  reaction  of  the  various  spe- 
cies unlike,  but  individuals  of  the  same  species  from  different 
localities  differ  widely.  (Cf.  LOEW,  '85.) 

We  are,  naturally,  most  familiar  with  this  phenomenon  in 
the  case  of  man.  Thus,  the  common  North  American  poison 
ivy  (Rhus  toxicodendron)  produces,  in  some  persons,  extensive 
inflammation  in  parts  which  have  come  even  indirectly  in  con- 


28        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

tact  with  it ;  while,  by  other  persons,  it  may  be  taken  into  the 
mouth  with  impunity. 

The  phenomenon  shown  by  man  is  found  in  other  animals 
also.  Thus,  among  Invertebrates,  although  few  bacteria  can 
resist  1%  .Na2CO3,  and  even  the  extremely  resistant  Ascaris 
lives  only  5  to  6  hours  in  a  5.8%  solution  of  this  salt,  LOE\V 
('77,  p.  137)  has  found  in  Owen's  Lake,  California  (an  alkaline 
water  containing  among  other  things  2.5%  Na2CO3),  numerous 
living  Infusoria,  Copepoda,  larvae  of  Ephydra,  and  molds. 
Again,  the  vinegar  eel,  Rhabditis  aceti,  lives  in  a  4%  solution 
of  acetic  acid,  although  this  strength  is  usually  fatal ;  e.g.  a 
0.23%  solution  of  acetic  acid  kills  the  tentacles  of  Drosera. 
(DARWIN,  '75,  p.  191.) 

What  is  true  of  the  whole  organism  is  true  also  of  its  parts. 
The  gland  cells  of  some  marine  Gasteropoda  (Dolium,  Cassis, 
Tritonium,  Natica  heros)  secrete  H2SO4  of  a  strength  (2%  to 
3%)  which  is  fatal  to  most  protoplasm;  the  myriapod  Foiitaria 
excretes,  when  irritated,  the  extremely  poisonous  CHN;  and, 
according  to  LOEW  ('87,  p.  438),  the  plant  Oxalis  produces 
potassic  oxalate,  which  is  a  violent  poison  to  most  protoplasm. 

One  general  law  of  high  resistance  is  worthy  of  notice:  an 
organism  which  produces  an  albuminoid  poison  is  strongly 
resistant  to  that  poison.  Thus,  FAYRER  ('74)  has  shown  that 
venomous  serpents  are  not  destroyed  by  the  secretion  of  their 
poison  glands  when  it  is  injected  into  them  ;  and  BOURNE 
('87)  has  shown  that  scorpions  are  not  injured  by  their  own 
venom. 

An  explanation  of  the  facts  of  varied  resistance  capacity  is 
first  gained  through  experiment.  We  all  know  that,  among 
men,  a  high  resistance  capacity  to  a  poison  may  be  acquired  by 
taking  a  small  quantity  of  it  at  frequent  intervals.  Thus, 
users  of  tobacco,  alcohol,  and  various  alkaloids  become,  in  time, 
capable  of  taking,  without  apparent  injury,  quantities  which 
would  at  first  have  proved  fatal.  Arsenic  eaters  may  eventu- 
ally swallow  without  injury  four  times  the  ordinarily  lethal 
dose,  i.e.  as  much  as  0.4  gramme.  (BiNZ  and  SCHULZ,  '79.) 

Results  similar  to  those  observed  in  man  have  been  obtained 
by  experiment  upon  other  animals.  Thus,  SEWALL  ('87) 
inoculated  a  pigeon  hypodermically  with  sub-lethal  doses  of 


ACCLIMATIZATION   TO   CHEMICAL   AGENTS 


29 


rattlesnake  poison  (Crotalophorus  tergeminus).  While  no 
unacclimatized  pigeon  could  resist  1  drop  of  a  6.8%  solution  of 
venom  in  glycerine,  pigeons  inoculated  with  at  first  weak,  then 
gradually  increasing  solutions,  came  at  last  (after  178  days)  to 
resist  4  drops  of  the  glycerine  venom  mixture.  Likewise  KAN- 
THACK  ('92)  succeeded  in  acclimatizing  two  rabbits  and  a  hen 
to  serpent's  venom. 

Very  similar  are  the  experiments  of  EHRLTCH  ('91).  This 
investigator  fed  white  mice  (which  are  killed  by  ^j-  of  their 
weight  of  a  0.0005%  solution  of  ricin,  hypodermically  in- 
jected) upon  food  cakes  soaked  in  a  weak  solution  of  the  poison. 
After  feeding  them  for  a  varying  length  of  time  upon  constantly 
increasing  solutions,  he  determined  the  maximum  solution 
which,  hypodermically  injected,  they  would  withstand.  If  we 
call  the  maximum  solution  which  the  unacclimatized  organism 
will  withstand  our  unit  of  immunity,  we  can  express  the  degree 
of  immunity  of  the  acclimatized  organisms  by  the  strength  of 
solution  (expressed  in  terms  of  that  unit)  which  they  can  resist. 

The  following  table,  taken  from  EHKLICH'S  paper,  shows 
the  gradual  increase  of  immunity  as  a  result  of  feeding  on  the 
poison  :  — 

TABLE   IV 


No.  OF  EXPERIMENT 
DAY. 

STRENGTH  OF 
LAST  DOSE  GIVEN. 

LN    MG. 

NUMBER  OF  INDI- 
VIDUALS EXPERI- 
MENTED ON. 

MAXIMUM  IN- 
JECTED SOLUTION 

BORNE,  %'S. 

DEGREE  OF 
IMMUNITY. 

IV 

4 

8 

j  Die  in 

1 

V  

5 

16 

1  0.0005 
0.0007 

1.3 

VI  

6 

23 

0.0066 

13.3 

YII  

7 

5 

0.005 

10 

VIII          .      .  . 

8 

18 

0.01 

20 

x 

12 

9 

0.02 

40 

XII 

20 

3 

0.033 

66.6 

XV                .      . 

50 

1 

0.05 

100 

XVIII.  .      . 

80 

4 

0.1 

200 

XXI  

80 

1 

0.2 

400 

Thus  after  the  first  4  or  5  days  the   immunity  rapidly  in- 
creased;   so  that,  while   the   solution   of   oWoo~o   ^^s  norma^ 


30  CHEMICAL   AGENTS  AND  PROTOPLASM  [Cn.  I 


mice,  those  acclimatized  during  21  days  resist  yoVo  to 
occasionally  giro,  corresponding  to  a  grade  of  immunity  of  200 
to  800. 

By  fundamentally  similar  procedures  CALMETTE  ('94)  has 
rendered  rabbits  immune  to  the  action  of  strong  doses  of  the 
venom  of  Naja  tripudians  (cobra)  and  of  Pelias  berus. 

Still  more  recently  MARMIER  ('95)  has  isolated  a  toxin 
produced  by  anthrax  bacteria  reared  in  a  peptone-glycerine 
solution.  Inoculated  into  an  animal  sensitive  to  anthrax, 
this  toxin  produces,  in  certain  doses,  death  by  cachexy.  By 
employing  suitably  graduated  doses,  however,  one  can  obtain 
immunity  of  the  organism  to  anthrax,  as  one  does  to  the  venom 
of  serpents. 

Some  attempts  to  produce  acclimatization  in  lower  organisms 
have  been  made  by  Dr.  H.  V.  NEAL  and  myself.  Stentor  was 
employed  as  the  object  of  experimentation.  We  reared  two 
lots  of  Stentors  under  similar  conditions  except  that  Lot  1  was 
cultivated  in  water  and  Lot  2  in  0.00005%  HgCl2.  After  the 
lapse  of  two  days  both  were  put  into  a  killing  solution  of 
0.001%  HgCl2,  and  the  second  lot  was  found  to  survive  longer 
than  the  first.  The  mean  resistance  period  to  the  killing  solu- 
tion of  the  lot  reared  in  water  was  83  seconds;  of  that  reared 
in  0.00005%  corrosive  sublimate,  304  seconds.  Similar  results 
were  obtained  in  other  experiments.  In  Fig.  1  a  curve  is 
given  showing  the  relation  between  strength  of  culture  solu- 
tion and  period  of  resistance.  From  this  curve,  based  upon 
132  determinations,  it  appears  that  the  resistance  period  varies 
directly  with  the  strength  of  the  solution  in  which  the  protoplasm 
has  been  cultivated. 

This  law  holds  good,  however,  only  within  certain  limits. 
If  the  culture  solution  is  too  strong,  above  0.0001%,  the 
organism  will  be  weakened  by  it  so  that  it  cannot  resist  the 
killing  solution  so  long  as  those  reared  in  water  can. 

A  similar  effect  of  heightened  resistance  to  quinine  is  ob- 
tained by  cultivating  organisms  in  quinine. 

Experiment  shows  that  a  slight  increase  of  the  resistance 
period  follows  subjection  to  the  culture  for  one  hour  only;  and 
that  the  degree  of  acclimatization  varies  directly  as  the  time 
of  subjection. 


„ 


ACCLIMATIZATION  TO   CHEMICAL  AGENTS 


31 


The  facts  obtained  by  us  clearly  indicated,  then,  that,  without 
selection,  —  for  no  deaths  occurred  in  our  culture  solutions, — 
the  protoplasm  may  become  modified  merely  by  subjection  to  the 
poison,  so  as  to  gain  an  increased  resistance  to  it.  Hence 
the  acclimatizations  that  we  find  in  nature  need  not  have 
been  brought  about  by  natural  selection  —  must  have  occurred, 
indeed,  even  without  selection,  if  the  organisms  had  been 
gradually  subjected  to  their  environment. 


\ 


90  SECS. 


70     1 


.50 


40  SECS. 


STRENGTH  OF  CULTURE  SOLUTIONS 

FIG.  1.  —  Curve  of  resistance  periods  to  a  0.00125%  solution  of  HgCl2  of  Stentors 
reared  in  various  solutions  of  HgCl2  during  20  to  96  hours. 

We  did  not  determine  for  how  long  a  time  the  acclimatized 
Protozoa  retained  their  heightened  resistance  capacity.  The 
only  data  we  have  upon  the  subject  of  persistence  of  acclima- 
tization is  derived  from  studies  on  Vertebrates. 

Thus  it  is  the  familiar  experience  of  arsenic  eaters  that,  after 
they  have  broken  off  their  habit,  the  body  does  not  quickly 
return  to  a  normal  condition.  Even  after  a  considerable  period 
of  self-denial  the  taking  of  large  doses  may  be  recommenced  — 
must  be  recommenced,  indeed,  or  illness  sets  in. 

EHBLICH  ('91)  has  studied  experimentally  the  phenomenon 


32        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

of  acclimatization  to  ricin.  Mice  which  had  gained  an  immu- 
nity of  over  200,  and  were  then  kept  for  6.5  months  on  normal 
food,  had  still  a  resistance,  although  not  precisely  determined, 
certainly  far  above  50. 

It  is  an  important  question :  Is  an  organism  acclimated  to 
one  poison  thereby  rendered  more  resistant  to  poisons  in  gen- 
eral, or  only  to  the  specific  poison  to  which  it  has  been  accli- 
mated? EHRLICH  found  that  mice  acclimated  to  ricin  were 
just  as  sensitive  to  abrin  as  the  normal  animals,  and  the  same 
is  true,  mutatis  mutandis,  for  mice  which  resist  abrin. 

Concerning  the  changes  in  the  protoplasm  brought  about  by 
acclimatization  little  is  known. 

EHRLICH  ('91)  and  CALMETTE  ('94)  have  shown  that  in  the 
blood  of  the  immunized  animal  a  substance,  antitoxic  to  the 
specific  substance  employed,  is  produced,  and  this  apparently 
prevents  the  action  of  the  strong  poison  by  transforming  its 
molecules.  The  antitoxic  substance  is  of  such  a  nature  that 
when  blood  containing  it  (from  an  acclimatized  animal)  is 
injected  into  an  unacclimatized  one,  the  latter  becomes  immune 
to  the  poison. 

For  Protista  another  hypothesis  is  admissible  ;  namely,  that 
the  weak  solution  of  the  poison,  which  is  used  in  acclimatiza- 
tion, gradually  destroys  those  compounds  upon  which  the 
strong  solution  would  have  acted  suddenly  and,  therefore, 
fatally.  The  gradual  destruction  is  not  fatal  because  of  its 
slowness.  At  the  same  time  it  prevents  the  violent  action  of 
the  strong  poison,  since  it  leaves  it  nothing  to  be  acted  upon. 

The  parallelism  between  the  results  of  experiments  upon 
acclimatization  to  poisons  and  those  upon  immunization  through 
vaccination,  leads  to  the  suspicion  that,  at  bottom,  the  two 
processes  are  closely  akin. 

§  3.    CHEMOTAXIS 

ENGELMANN  ('81)  seems  to  have  been  the  first  to  show  that 
the  direction  of  locomotion  of  simple  protoplasmic  masses  is  de- 
terminable  by  chemical  agents  in  the  environment.  He  found 
that  Bacterium  termo  is  thus  acted  upon  by  oxygen  which  is 
not  uni'formly  distributed.  Like  many  Infusoria,  these  bacteria 


§  3]  CHEMOTAXIS  *  33 

gather  at  the  margin  of  the  cover-glass,  where  oxygen  is  more 
abundant  than  elsewhere.  If  oxidized  blood  is  introduced 
under  the  cover-glass,  they  move  toward  it,  but  not  toward 
blood  containing  much  CO2  in  place  of  oxygen.  If  green 
algie  are  introduced,  the  bacteria  move  towards  them  so  long 
as  they,  under  the  influence  of  sunlight,  are  producing  oxygen. 
In  the  dark  the  algae  have  no  effect. 

During  the  decade  and  a  half  which  have  elapsed  since  Ex- 
GELMAXN'S  first  paper  appeared,  chemotactic  phenomena  have 
been  observed  among  nearly  all  kinds  of  motile  organisms  and 
with  reference  to  the  most  diverse  kinds  of  chemical  substances. 
EXGELMAXX  ('82)  has  studied  the  chemotactic  movements  of 
diatoms ;  STAHL  ('84),  of  Myxomycetes ;  PFEFFER  ('84,  '88), 
of  plant  spermatozoids,  zoospores,  Flagellata,  Infusoria,  and 
bacteria  ;  ADERHOLD  ('88),  of  Euglena  viridis ;  VERWORN 
('89,  p.  107),  of  Cryptomonas ;  STAXGE  ('90),  of  zoospores  and 
Myxomycetes ;  and  MASSART  ('91),  of  Spirillum,  Heteromita, 
and  Ciliata. 

Within  the  last  five  years  a  voluminous  literature  has  grown 
up  on  the  medical  side  relating  to  chemotaxis  in  leucocytes  and 
pathogenic  bacteria.  Into  this  literature  we  cannot  penetrate 
deeply,  but  refer  to  some  of  the  principal  papers  :  LEBER,  '88  ; 
BUCHXEE,  '91 ;  ROEMER,  '92  ;  METSCHNIKOFF,  '92. 

It  thus  appears  that  chemotactic  phenomena  show  themselves 
among  all  the  groups  of  lower  motile  organisms  :  Rhizopoda 
(Myxomycetes),  Flagellata,  Ciliata,  bacteria,  diatoms,  zo- 
ospores, and  sperinatozooids.  It  can  hardly  be  questioned  that 
the  phenomena  shown  by  these  organisms  are  of  the  same  order 
as  those  seen  in  Metazoa  —  in  those  ants  which  LUBBOCK  ('84, 
p.  283)  has  shown  to  move  from  chemical  agents  (essence  of 
cloves,  lavender  water,  and  other  scented  stuffs),  saturating  a 
camel's-hair  brush  placed  about  ^  inch  above  their  path  ;  and 
in  the  larvae  of  flies  with  which  LOEB  ('90,  p.  79)  has  experi- 

•nted.  LOEB  found  that  these  crept  towards  a  piece  of  flesh 
brought  nearer  to  them  than  the  distance  of  1.5  cm.  Even  just 
hatched  larvae  (which  had  therefore  never  been  stimulated  by 
meat)  reacted  in  this  way.  Not  meat  only,  but  a  trace  of  meat 
juice  on  glass  attracted  the  larvae  strongly.  A\7hile  decaying  flesh 
;  and  cheese  allure,  neither  fat,  asafoetida,  nor  ammonia  do  so. 

!> 


34  CHEMICAL  AGENTS  AND  PROTOPLASM  [Cn.  1 

Returning  now  to  the  simple  organisms,  let  us  consider  the 
kinds  of  chemical  substances  which  incite  to  a  response. 

Oxygen  is  for  almost  all  organisms  a  means  of  attraction. 
Various  methods  of  demonstrating  this  have  been  used.  Thus 
STANGE  ('90,  p.  139)  filled  capillary  tubes  with  pure  oxygen, 
under  an  air-pump,  and  brought  them  to  the  water  containing 
zoospores,  which  then  penetrated  into  them. 

The  aggregation  of  zoospores  and  bacteria  to  the  edges  of 
the  cover-glass,  to  the  open  end  of  a  capillary  tube  (ADEKHOLD, 


Air  bubble 


/# 

,  Zone  of  Spirillum     **'  ;V 


Zone  0/  Anophrys  .  .  *'«    *• 


V^35^    A 

Gt,.  VV.-:V:^C.T.::;V^ 

FIG.  2.  —  a.  Corner  of  the  glass  slip  covering  a  drop  of  liquid  containing  Spirillum 
and  Anophrys,  showing  their  aggregation  with  reference  to  the  aerated  bound- 
ing film  of  the  drop.  b.  An  air-bubble  in  the  drop,  showing  aggregation  of  the 
organisms  about  it.  (From  MASSART,  '91.) 

'88,  p.  314),  or  to  an  enclosed  air-bubble,  are  well-known  phe- 
nomena. (Cf .  MASSART,  '91,  p.  159 ;  VEEWOEN,  '89,  p.  107 ; 
and  see  Fig.  2.) 

ENGELMANN  ('94)  has  employed  a  still  more  refined  method 
of  studying  attraction  towards  oxygen.  A  drop  of  foul  water 
is  put  on  a  glass  slide  with  an  alga  cell  in  the  centre,  and  is 
covered  by  a  cover-glass  whose  edges  are  hermetically  sealed 
by  vaseline.  The  bacteria  are  uniformly  distributed  in  the 
water,  moving  in  a  lively  manner,  since  they  gain  oxygen 
everywhere.  If  the  slide  thus  prepared  is  kept  in  the  dark, 
the  oxygen  is  gradually  consumed  and  the  bacteria  become 
quiescent,  showing  no  distribution  with  reference  to  the  cen- 
tral chlorophyllaceous  body  (Fig.  3). 

If  the  slide  is  now  exposed  to  the  light,  oxygen  is  produced 
by  the  alga  and  a  regular  distribution  of  the  bacteria  in  two 
distinct  regions  —  in  a  mass  around  the  central  alga,  and  in  a  i 


§  3] 


CHEMOTAXIS 


35 


peripheral  zone  —  is  apparent  (Fig.  4).  The  peripheral  zone 
contains  bacteria  which  are  beyond  the  tactic  action  of  the 
oxygen.  The  central  mass  of  bacteria  have  emigrated  from 
what  is  now  a  clear  ring  between  the  centre  and  the  peripheral 
zone.  If  the  light  be  temporarily  cut  off,  the  central  bacteria 


V*^  •;."'*-'  ".'^1? 


;0v',.^'  -:5ft 

*•":'.'•/    r   .    ".*7»7  .    .  » .y'«V/ 

^»-   •  *..  *       .  •-• 


«•.*;. « 
»*  .  ..»\s 


, .  •.  ••• 
^fv?:* 

''V;  r»*"f/:V"C 

4 


?^:f  'W.Hk-li:.'  .V*3 

i^^l'wr  ^ 

:^.%fv--i»-    ^ 

•{^KV       o'^^^'     -^- 


FIGS.  3-5 a.  —  Bacteria  surrounding  an  algal  cell.  Fig.  2  shows  the  uniform  distribu- 
tion of  the  bacteria  \vhen  the  drop  of  water  is  kept  in  the  dark.  Fig.  3  shows  the 
aggregation  of  the  bacteria  towards  the  algal  cell  when  this  has  emitted  oxygen 
rapidly  in  the  strong  light  for  two  minutes.  Fig.  4  shows  the  same  preparation 
shortly  after  the  light  has  been  cut  off.  Fig.  5  shows  the  same  preparation  when 
a  fainter  light  is  now  permitted  to  fall  upon  the  green  cell.  Magnified  about  170 
diameters.  (From  ENGELMANX,  '94.) 

begin  to  disperse  (Fig.  o).  If,  a  minute  after,  a  dim  light  be 
let  through,  the  radius  of  its  activity  will  be  relatively  small,  so 
that  a  central  aggregation  will  be  found  and  also  an  inner 
peripheral  zone,  comprising  those  dispersing  central  bacteria 
which  are  not  affected  by  the  small  oxygen  tension  resulting 
from  the  dim  light  (Fig.  5  a). 


36        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

Inorganic  Salts.  —  PFEFFER*  ('88,  p.  601)  tried  various  salts 
of  potassium;  viz.  chloride,  phosphates,  nitrate,  sulphate,  car- 
bonates, chlorate,  ferrocyanide,  and  tartrate,  and  found  that 
all  attracted  various  bacteria  (B<  termo,  Spirillum  undula), 
and  the  flagellate  Bodo  saltans  with  greater  or  less  strength, 
when  the  solution  in  the  capillary  tube  contained  0.1%  K.  So, 
likewise,  various  salts  of  sodium,  rubidium,  caesium,  lithium, 
ammonium,  calcium,  strontium,  barium,  magnesium,  especially 
the  chlorides,  were  employed.  All  of  these  solutions  at  a 
concentration  of  0.5%  exhibited  a  marked  attractive  influ- 
ence upon  Bacterium  termo ;  a  weaker  one,  upon  the  two 
other  species. 

STANGE  ('90)  experimented  with  the  action  of  various  phos- 
phates upon  zoospores  of  a  Saprolegnia  belonging  to  the  ferax 
group  of  DE  BARY.|  Sodic,  ammonic,  lithic  phosphate,  calcic 
phosphate  held  in  solution  by  CO2,  as  well  as  phosphoric  acid 
were  employed  and  found  to  act  attractively.  Other  salts, 
KNO3,  K2SO4,  KC1,  HKCO3,  BaClO3,  SrCO3,  MgSO4,  had 
either  a  negative  or  indifferent  action  upon  the  zoospores. 

The  attractive  action  of  the  phosphates  is  correlated  with 
the  fact  that  phosphates  are  abundant  in  the  muscles  of  insects. 
The  following  table  shows  the  effect  of  the  different  strengths 
of  solutions  of  four  phosphates  upon  zoospores  of  Saprolegnia. 
In  this  table,  constructed  from  STANGE,  the  symbol  r  indicates 
repulsion ;  0,  no  action ;  a,  attraction  ;  a^  indicates  a  slight 
attraction  ;  #2,  a  strong  attraction  ;  a2rv  an  attraction  which 
is  partly  balanced  by  a  repulsion  due  to  density,  so  that  the 

*  The  method  employed  by  PFEFFER  in  his  experiments  was  as  follows : 
Glass  capillary  tubes  with  a  lumen  of  from  0.03  to  0.14  mm.  diameter  and  a 
length  of  7  to  12  mm.,  and  sealed  by  fusion  at  one  end  were  employed.  To  fill 
the  capillary  tube,  it  was  placed  in  a  watch-glass  containing  the  experiment  solu- 
tion, and  the  whole  was  placed  in  a  vessel  from  which  air  was  pumped.  Under 
the  diminished  atmospheric  pressure,  2  to  4  mm.  of  fluid  entered  the  capillary 
tube ;  the  rest  of  the  tube  contained  air,  which  kept  the  fluid  oxidized.  After 
rinsing,  the  free  end  of  the  tube  was  plunged  into  the  drop  culture,  whence  the 
solution  diffused  out. 

t  The  species  were  cultivated  upon  carcasses  of  flies  thrown  into  glasses  filled 
with  bog  water.  After  good  colonies  were,  obtained,  the  carcasses  were  washed, 
to  rid  of  Infusoria.  Such  colonies  may  be  employed  to  infect  sterilized  flies' 
legs  placed  in  sterilized  bog  water,  or  they  may  be  transferred  directly  to  wounds 
in  flies'  legs. 


,. 


CHEMOTAXIS 


37 


organisms  pass  only  into  the  first  part  of  the  tube  ;  «3r3,  such 
a  balancing  of  the  opposing  forces  that  the  organisms  stand 
before  the  mouth  of  the  capillary  tube. 


STP.EXGTH  OF  SOLUTION, 

C"     'c 

SODIC  DIPHOS- 

PHATE 

POTASSIC  MONO- 
PHOSPHATE 

AMMONIUM  PHOS- 
PHATE 

PHOSPHORIC 
ACID 

70  °- 

(HXa2P04). 

(H2KP04). 

(H2NH4P04?). 

(HSP04). 

0.8      to  0.4  .... 

«3r2 

a3r2 

asr3 

r 

0.4      to  0.08    .   .   . 

°2rl 

Ofl 

0.08    to  0.04    .   .   . 

«2 

a, 

°2 

air2 

0.01    to  0.02    .   .   . 

0 

ai 

°1 

fllrl 

0.02    to  0.008  .   .   . 

0 

0 

«2 

0.008  to  0.004  .   .   . 

ai 

0.004  to  0.002  .   .   . 

0 

It  will  be  noticed  that  the  various  substances  produce  dif- 
ferent effects  in  the  same  strength  of  solution ;  and  it  is 
interesting  to  observe  (a  point  to  which  further  reference  will 
be  made)  that  the  strength  of  solution  required  to  produce  a 
given  response  is  roughly  proportional  to  the  molecular  weight 
of  the  substance  employed. 

Inorganic  acids  and  hydrides  seem,  in  general,  to  act  repul- 
sively, but  phosphoric  acid  is  an  important  exception  to  this 
rule.  DEWITZ  ('85,  pp.  222,  223)  states  that  mammalian 
spermatozoa  are  attracted  by  KHO. 

Organic  Compounds. — Alcohol,  in  grades  between  10%  and  1%, 
acts  repulsively  towards  bacteria.  G-lycerine  is  neutral  to  the 
same  organisms  and  to  zoospores  of  Saprolegnia.  (STANGE,  '90.) 
The  sugars,  etc.,  dextrose,  milk  sugar,  dextrin,  act  attractively 
upon  Bacterium  termo  in  10%  or  weaker  solutions.  Many  or- 
ganic acids  are  among  the  most  attractive  reagents.  It  was  with 
malic  acid  that  PFEFFEK  ('84)  tried  his  earlier  fundamental 
experiments  upon  the  spermatozoids  of  ferns.  The  attraction 
exerted  is  very  great,  so  that  a  capillary  tube  of  0.1  to  0.14  mm. 
calibre,  containing  a  0.05%  solution  of  malic  acid,  attracts 
from  a  drop  of  water  full  of  spermatozoids  at  the  rate  of  100 
individuals  in  one  hour.  Even  a  0.001%  solution  acts  chemo- 
tactically.  Now,  malic  acid  is  of  very  wide  distribution  among 
plants,  and  it  occurs  in  the  fern  prothalli  upon  which  the  sexual 


38        CHEMICAL  AGENTS  AND  PROTOPLASM      [Cn.  I 

organs  arise,  so  that  it  seems  probable  that  it  occurs  in  the 
mouth  of  the  archigonium,  and  that  by  its  presence  sperma- 
tozoids  are  attracted  towards  the  egg  cell. 

STANGE  ('90,  p.  155)  has  experimented  much  more  fully 
with  the  action  of  organic  acids  upon  zoospores  of  Saprolegnia 
and  upon  myxamcebse.  To  the  former,  acetic  acid  (0.01%)  and 
tartaric  acid  (0.0125%)  act  attractively.  Upon  the  latter,  still 
other  acids  were  tried;  butyric,  lactic,  and  valeric  acids  cause 
response  in  concentrations  between  0.2%  and  4%  ;  malic  acid, 
between  0.5%  and  4%.  Other  attracting  acids  are  :  propionic, 
citric,  tartaric,  and  tannic.  Acetic  acid  repels  the  amoebae  of 
JEthalium,  its  repellent  action  being  about  equal  to  the  attrac- 
tive action  of  an  equal  amount  of  butyric  acid. 

Nitrogenous  Compounds.  —  Urea,  asparagin,  kreatin,  taurin, 
hypozanthin,  carnin,  and  peptone  have  been  found  by  PFEFFER 
('88)  to  exert  an  attractive  influence,  especially  in  the  case  of 
the  reagents  italicized. 

Benzol  Derivatives. — PFEFFER  found  that  sodium  salicylicate 
and  (commercial)  sulphate  of  morphine  are  clearly  attractive  to 
Bacterium  termo  in  1%  solutions. 

From  the  foregoing  list  of  organic  compounds  whose  effect 
upon  Protista  has  been  tested  by  PFEFFER  and  STANGE,  it 
appears  that  except  alcohol  and  sometimes  acetic  acid,  none 
acts  repulsively,  and  that  glycerine  alone  is  neutral  to  all  proto- 
plasm. It  is  further  true  that  we  do  not  find  here  any  strict 
relation  between  the  chemotactic  action  of  a  substance  and  its 
advantage  to  the  organism.  Substances  which  have  a  nutri- 
tive value  for  the  organism,  such  as  glycerine  has  for  bacteria, 
may  be  wholly  neutral,  while  solutions  which  act  fatally,  like 
1%  sodic  salicylicate  and  1%  morphine,  attract.  In  the  same 
way,  many  of  the  organic  salts  which  act  attractively  cannot 
be  considered  as  of  importance  to  the  organism.  On  the  other 
hand,  as  already  pointed  out,  the  attraction  of  most  Protista  to 
oxygen,  of  Saprolegnia  zoospores  to  phosphates,  as  well  as  the 
cases  of  attraction  of  bacteria  (PFEFFER,  '88,  p.  605)  and  of  fly 
larvae  (LoEB,  '90,  p.  79)  to  meat  extract,  and  of  Myxomycetes 
to  bark  extract  (STAHL,  '84 ;  STANGE,  '90),  is  advantageous. 
Chemotaxis  is,  therefore,  in  some  cases,  a  response  to  the 
stimulus  afforded  by  substances  which  can  be  employed  by 


„ 


CHEMOTAXIS  39 


the  organism  as  food ;  under  which  circumstances  it  can  be 
called  "  Trophotaxis."  *  In  other  cases  it  is  a  response  to 
chemical  substances  which  have  no  significance  as  food,  and 
have  no  other  importance  for  the  organism. 

It  is  clear  that  we  cannot  assume  that  response  to  injurious 
substances  is  an  adaptation  which  has  been  brought  about  by 
natural  selection.  If  a  response  occurs  in  one  case  independent 
of  the  action  of  selection,  we  should  hesitate  to  ascribe  to  this 
cause  the  origin  of  other,  even  favorable,  responses. 

General  Remarks  on  the  Relation  between  Molecular  Composi- 
tion and  Response.  —  PFEFFEB,  ('88,  pp.  608-612)  has  pointed 
out  that  the  capacity  of  any  substance  to  stimulate  cannot  be 
inferred  from  its  chemical  constitution  and  relationships.  Thus, 
the  minimum  congentration  of  milk  sugar  which  will  produce 
a  response  is  1%,  while  in  the  case  of  the  closely  allied  grape 
sugar  it  is  10  %  ;  but  in  the  very  different  kreatin  it  is  also  1  %  • 
Also,  the  action  of  any  chemical  compound  is  determined  not 
by  the  elements,  such  as  C,  H,  O,  which  it  contains,  but  by  the 
entire  molecule  ;  in  other  words,  the  atomic  composition  is  less 
important  than  the  structure  of  the  molecule  or  the  arrange- 
ment of  its  atoms.  Thus,  malic  acid  and  its  compounds  with 
neutral  ammonium,  sodium,  barium,  and  calcium  containing 
0.001%  parts  of  the  acid,  have  an  equal  action  upon  the  sperma- 
tozoids  of  ferns,  which  do  not  react  to  the  diethylester  of 
malic  acid,  even  in  strong  solutions.  (PFEFFER,  '88,  p.  655.) 
Again,  nitrogenous  organic  compounds  are,  in  general,  more 
active  than  the  non-nitrogenous  ones  ;  but  this  cannot  be  held 
to  be  due  alone  to  the  presence  of  N ;  for  dextrin  (C6H10O5) 
is  nearly  as  active  as  the  nitrogenous  peptone,  and,  on  the  other 
hand,  the  nitrates  of  metals  are  not  more  active  than  their 
chlorides,  while  the  ammonia  salts  are  relatively  weak. 

Relation  between  the  Strength  of  the  Stimulus  and  that  of  the 
Response.  —  When  we  say  that  malic  acid  attracts  sperma- 
tozoids  we  mean  that  under  certain  physical  conditions  of 
the  water  which  we  may  call  normal  it  does  so.  And  under 
normal  conditions  of  the  water,  it  is  only  within  certain  limits 


*  STAHL  ('84,  p.  164)  called  the  attraction  of  plasmodium  of  myxomycetes  to 
bark  extract  "  Trophotropism." 


40        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

that  malic  acid  attracts.  The  strengths  of  solutions  which 
attract  under  such  conditions  lie  between  0.001%  and  10%. 
The  weaker  solution  may  be  designated  the  minimum ;  the 
stronger,  the  maximum  concentration  which  provokes  a  re- 
sponse. The  minimum  solution  provoking  response  is  also 
often  called  by  the  Germans  the  " Reizschwelle,"  or  "stimula- 
tion threshold  "  ;  *  the  optimum,  the  "  Reizhohe,"  or  "  stimu- 
lation acme";  the  range,  the  "Reizumfang." 

The  character  of  the  responses  observable  at  the  two  limits 
is  very  different ;  at  the  minimum,  attraction  is  very  feeble ; 
thus,  while  a  capillary  tube  containing  0.01%  neutral  sodic 
malate,  plunged  into  water  at  14°-20°  C.,  swarming  with 
spermatozoids,  attracts  400  of  them  in  10  minutes,  a  0.001% 
solution  attracts  only  10-25  individuals  during  the  same  time, 
and  a  0.0008%  exerts  little  attractive  effect,  the  spermatozoids 
remaining  undirected  in  their  movements.  At  the  maximum, 
on  the  contrary,  repulsion  is  observed.  The  spermatozoids 
move  from  the  mouth  of  the  capillary  tube.  Between  the 
two  extremes  lies  the  concentration  of  greatest  attraction  — 
the  acme.  As  we  pass  from  the  acme  towards  the  minimum, 
the  attraction  becomes  less  and  less.  As  we  pass  towards  the 
maximum,  the  attraction  remains  the  same,  or  increases ;  but 
repelling  influences  are  now  at  work,  which  eventually  entirely 
counteract  the  attractive  influences. 

A  satisfactory  method  of  expressing  quantitatively  the  facts 
just  mentioned  has  not  been  invented.  PFEFFER  ('88,  p.  599) 
has  employed  the  nomenclature  which  we  have  used  above 
(p.  36)  —  a±  to  as  being  combined  with  r1  to  rs  to  indicate 
the  coworking  in  varying  proportions  of  attraction  and  repul- 
sion. Using  this  nomenclature,  we  may  illustrate  the  state- 
ments made  in  the  last  paragraph  with  examples  taken  from 
PFEFFER'S  work:  — 


*  The  following  substances  at  the  solutions  named  produce  the  threshold 
attraction  («i)  in  Bodo  saltans:  KC1,  0.02%;  K3PO4,  0.002%;  KH2PO4, 
0.0035%;  KN03,  0.26%;  K2S04,  0.22%;  KC103,  0.3%;  K4(CN)6Fe,  0.235%; 
K2.C4H406,  0.02%;  BbCl,  0.14%;  LiCl,  0.6%;  LiN03,  3%;  NH4C1,  0.3%; 
neutral  ammonium  phosphate,  0.08%;  SrCl2,  0.2%;  Sr(N03)2,  0.4%;  BaCl2, 
0.17%;  dextrin,  0.1%;  urea,  1%;  asparagin,  0.1%;  taurin,  1%;  sarkin, 
0.33%;  pepton,  0.01%;  meat  extract,  0.01%. 


CHEMOTAXIS 


41 


GRADE  OF  SOLUTION. 

EESPOXSE  OF 

BACTERIUM  TERMO. 

SPIRILLUM. 

9.53  %  KC1 

=  5%K 

a3 

a3r 

1.906  %KC1 

=  1%K 

«3 

«3ri 

0.191  %  KC1 

=  0.1%  K 

°3 

an 

0.019  %  KC1 

=  0.01%K 

«2 

ai 

0.0019  %  KC1 

=  0.001  %  K 

«1 

0 

BODO  SALTASS. 

3.48  %  KH2PO4 

=  1.0%K 

a3r3 

0.348  %KH2PO4 

-  0.1  %K 

<*3r2 

• 

0.035  %KH.,PO4 

=  0.01%K 

a2 

0.0035  %KH2PO4 

=  0.001  %  K 

ai 

0.00067  %  KH2PO4 

=  0.0002  %K 

0 

Compare  also  the  table  on  p.  37. 

For  all  reagents  which  exert  an  attractive  influence  there 
exists  the  maximum  (repelling)  and  minimum  (indifferent) 
limits  referred  to.  In  the  case  of  reagents,  which,  like  alco- 
hol, repel  bacteria  at  between  1%  and  10%,  there  is  doubtless 
an  indifferent  limit,  but  it  is  not  necessary  that  there  should  be 
a  degree  of  concentration  at  which  attraction  takes  place.  In 
the  one  case,  then,  the  phenomena  of  indifference,  attraction, 
repulsion,  follow  each  other  with  increasing  concentration ;  in 
the  other  case,  only  indifference  and  repulsion.  The  difference 
in  action  of  the  two  cases  is  due,  in  part  at  least,  to  the  fact 
that  all  solutions,  independently  of  their  chemical  constitution, 
become  repellent  when  they  become  concentrated  enough. 
The  repulsion,  then,  of  high  grades  of  chemical  solutions  is 
purely  an  osmotic  phenomenon,  and,  as  such,  will  come  under 
discussion  in  the  third  chapter.  It  follows,  also,  from  what  has 
been  said,  that,  in  the  case  of  those  reagents  which  exert  no 
attraction  at  any  concentration,  the  acme  and  maximum  coin- 
cide and  lie  at  the  saturation  point  of  the  solution. 

Finally,  we  may  discuss  the  third  case  in  which  the  reagent 
acts  indifferently,  as  glycerine  does  upon  bacteria  between  17% 
and  0.86%.  It  is  clear,  that  if  the  density  of  the  solution  can 


42 


CHEMICAL  AGENTS  AND  PROTOPLASM 


[Cn.  1 


be  rendered  great  enough,  a  repulsion  due  to  osmosis  must 
occur.  If  the  substance  is,  however,  only  soluble  slightly  or 
miscible,  it  may  be  that  repulsion  will  never  occur.  Whether 
or  not  attraction  will  occur  before  the  repulsion  point  is  reached 
will  have  to  be  determined  experimentally  for  each  reagent. 

Thus  the  action  of  an  untried  substance  upon  any  organism 
may  be  any  one  of  three  kinds  :  (1)  It  may  be  indifferent  at 
all  grades;  (2)  it  may  be  indifferent  at  lower  and  repellent 
at  higher  grades ;  (3)  it  may  be  indifferent,  attractive,  and 
repellent  at  successive  grades.  Of  two  substances  belonging 
to  the  second  or  third  class,  one  may  act  upon  an  organism  at 
a  certain  concentration  with  indifference,  the  other  at  the  same 
concentration  with  repulsion.  Likewise  the  same  solution  of  a 
substance  may  attract  one  kind  of  protoplasm  and  repel  another, 
under  otherwise  similar  conditions. 

We  have  seen  above  that  the  same  reagent  acts  upon  the 
same  kind  of  protoplasm  similarly  only  when  the  other  con- 
ditions of  the  experiment  are  also  the  same.  Among  the 
varying  conditions  which  have  been  especially  investigated  is 
that  of  the  chemical  constitution  of  the  medium.  The  experi- 
ment has  generally  been  made  as  follows :  A  particular  species, 
let  us  say  Bacterium  termo,  is  to  be  subjected  to  the  action  of 
a  particular  reagent,  e.g.  meat  extract.  The  bacteria  are  reared 
in  cultures  containing  a  varying  quantity  of  the  meat  extract, 
and  the  concentration  of  the  capillary  fluid  producing  the 
threshold  stimulation  is  measured  in  each  case.  We  may 
compare  not  only  the  threshold  stimulations  but  also  the 
concentrations  necessary  to  produce  the  response  indicated 
by  av  «2,  etc.  The  following  table,  from  PFEFFER  ('88, 
p.  634),  gives  some  of  such  determinations:  — 


CULTURE  FLUID  — 
MEAT  EXTRACT. 

CAPILLARY  FLUID  —  MEAT  EXTRACT. 

3  x  cult.  cone. 

5  x  cult.  cone. 

8  x  cult.  cone. 

10  x  cult.  cone. 

0.01  % 

0.1% 

1% 

0.03  o/o  (?) 
0.8%  (?) 

3%(?) 

0.05  %(at) 
0.5%(0l) 
5%(«i) 

0.08%  (a,) 
0-8%  (a,) 
8%(«2) 

0.1%  (aj 

!%(«*) 

io%(«2) 

,. 


]  CHEMOTAXIS  43 

From  this  table  it  appears  that  the  strength  of  solution 
necessary  to  provoke  a  certain  response  depends  upon  the 
strength  of  solution  to  which  the  protoplasm  has  been  pre- 
viously subjected  and  increases  proportionately  with  it.  It  is 
clear  that  the  capillary  solution  of  0.1%,  which  produces  a 
marked  chemotaxis  in  bacteria  reared  in  a  culture  solution  of 
0.01%,  would  awaken  no  response  in  bacteria  reared  in  0.1%. 

We  are  now  in  a  position  to  appreciate  the  importance  of 
still  another  addition  to  our  terminology  of  stimuli  —  the  dif- 
ferential threshold  stimulation  (Reizunterscheidsschwelle)  — 
which  may  be  denned  as  the  minimum  increase  of  a  preexisting 
stimulus  which  is  capable  of  calling  forth  a  just  noticeable 
reaction.  In  the  case  just  cited,  the  differential  threshold 
stimulation  lies  just  above  3  times  the  preexisting  (culture) 
stimulus,  and  this  is  true  whatever  the  degree  of  the  preexist- 
ing stimulus  ;  and  it  is  shown  by  experiment  that,  in  general, 
as  the  preexisting  stimulus  increases,  the  differential  threshold 
stimulation  increases  in  the  same  proportion.  This  observa- 
tion is  in  perfect  accord  with  the  law  formulated  long  ago  bj 
WEBER  with  especial  reference  to  sight.  This  law  runs  :  The 
smallest  change  in  the  magnitude  of  a  stimulus  which  will  call 
forth  a  response  (differential  threshold  stimulation)  always 
bears  the  same  proportion  to  the  whole  stimulus.  We  may 
express  this  law  mathematically,  as  FECHNER  has  done,  by  the 
following  considerations  :  Let  us  take  the  case  of  a  protoplas- 
mic body,  as,  for  example,  that  of  a  spermatozoid,  living  in  a 
stimulating  medium  (s)  of  a  certain  concentration  and  experi- 
encing a  certain  reaction  rr ;  then  s  corresponds  to  r'.  In 
order  just  to  get  a  chemotactic  response  (threshold  stimulation), 
a  solution  of  say  30  times  the  concentration  must  be  brought 
to  the  solution  affording  the  stimulation  s.  This  will  give  a 
reaction  which  is  greater  than  r'  by  a  quantity  which  we  may 
designate  r,  so  that  the  quantity  of  the  whole  reaction  may  be 
designated  as  r'  +  r.  If  the  organisms  are  now  placed  in  this 
stronger  solution  (31  s),  the  solution  in  the  capillary  tube  must 
be  30  times  stronger  (30  x  31  s)  in  order  to  give  the  differential 
threshold  stimulation.  The  reaction  following  this  stimulation 
may  be  designated,  according  to  FECHNER 's  conception,  as 
r'  +  r  +  r.  The  relation  of  the  successive  stimuli  and  the  reac- 


44  CHEMICAL  AGENTS  AND   PROTOPLASM  [Cn.  I 

tions  may  be  shown  by  the  following  table,  following  one  given 
by  PFEFFER  ('84,  p.  401)  :  — 

s  corresponds  to  r'. 

s-f-  30s  =  31s  corresponds  to  r'+r. 

31s-f         30x31s=          31  x 31  s  corresponds  to  r'+r +r. 

31  x  31  s+30  x  31  x  31  s  =  31  x  31  x  31  s  corresponds  to  r'+r+r+r. 

That  is  to  say,  while  the  stimulation  increases  geometrically, 
the  reaction  increases  arithmetically.  In  the  preceding  table 
the  second  term  of  the  left-hand  member  of  the  equation  is 
always  the  differential  threshold  stimulation. 

The  most  important  objection  that  can  be  urged  against  this 
formula  of  FECHNEB  is  that  there  is  not  sufficient  reason  for 
believing  that  the  various  reactions  (r)  to  the  differential 
threshold  stimulations  of  various  strengths  are  equal,  nor  that 
the  stronger  reaction  to  the  strong  stimulus  is  composed  of 
many  weak  reactions.  If  these  assumptions  were  true,  it  would 
follow  that  when  the  successively  higher  stimuli  increase  as  a 
series  of  numbers  the  reactions  increase  as  the  logarithms  of 
these  numbers.  If  now  we  adopt  as  a  unit  in  this  phenomenon 
the  quantity  of  the  threshold  stimulation  (estimated  in  units  of 
concentration  of  solution,  of  mass,  light  intensity,  heat  inten- 
sity, etc.),  which  we  may  call  s,  the  strength  of  any  stimulus 
($)  may  be  estimated  in  those  units,  and  the  strength  of  the 
corresponding  reaction  (.72)  will  be  indicated  by  the  equation 
R  =  c  •  log  S,  in  which  c  is  a  constant  to  be  determined  empiri- 
cally, and  S  the  strength  of  the  stimulus  expressed  in  units  of 
the  threshold  stimulation.* 

While  we  are  not  yet  in  a  position  to  understand  the  signifi- 
cance of  WEBER'S  law,  we  cannot  fail  to  be  struck  with  the 
resemblance  of  the  phenomena  with  which  it  concerns  itself  to 
those  of  acclimatization  referred  to  in  the  second  section  of 
this  chapter.  We  there  showed  that  organisms  subjected  for  a 
while  to  a  chemical  agent  no  longer  reacted  as  at  first  to  that 
reagent.  We  have  here  shown  that  organisms  subjected  for 

*  Since  the  German  word  for  stimulus  is  Heiz  (initial  .R),  and  since  the  re- 
action is  usually  indicated  by  the  initial  letter  in  Empfindung,  in  German  text- 
books this  formula  usually  runs  E  =  c  •  log  7?,  which  differs  from  the  above 
equation  only  in  the  symbols  employed. 


SUMMARY  OF  THE  CHAPTER  45 

while  to  the  action  of  a  certain  stimulating  agent  respond  no 
longer  to  a  concentration  which  would  at  first  have  .provoked 
a  reaction.  In  both  cases  it  is  the  action  of  the  chemical  agent 
which  modifies  the  subsequent  action  of  the  protoplasm,  without 
doubt  by  changing  the  chemical  constitution  of  the  protoplasm. 

Mechanics  of  Response.  —  Having  considered  the  general 
relation  between  strength  of  stimulus  and  of  reaction,  it  now 
becomes  necessary  to  examine  more  in  detail  into  the  way  in 
which  the  reaction  takes  place. 

A  variety  of  kinds  of  locomotion  exists  among  chemotactic 
organisms  —  that  of  the  Myxomycetes  is  amoeboid,  that  of 
Infusoria  is  by  flagella  or  cilia.  In  all  cases  the  first  and 
perhaps  the  only  effect  of  the  acting  reagent  is  to  determine 
the  position  of  the  axis  of  the  body,  in  the  case  of  bodies  with 
fixed  form ;  or  to  determine  the  pole  of  outflow  in  the  case  of 
amoeboid  organisms.  The  axis  lies  in  the  line  of  flow  of  the 
diffusing  solution  or  perpendicular  to  the  isotonic  lines,  or  lines 
of  equal  concentration.  Whatever  movement  now  occurs  must 
be  either  towards  or  from  the  source  of  stimulus. 

I  have  said  above  that  the  axis  orientation  is  perhaps  the 
only  effect  of  the  acting  reagent.  PFEFFER  ('84,  p.  463 ;  '88, 
p.  631),  indeed,  maintains  that  the  stimulus  does  not  directly 
cause  a  markedly  more  rapid  locomotion  in  the  case  of  bacteria 
and  Flagellata ;  but  in  the  case  of  plasmodia  it  seems  possible 
that  such  a  hastening  of  movements  occurs.  (SxAHL,  '84.) 
However,  it  is  necessary  that  measurements  should  be  made  in 
this  matter.  Further  observations  on  the  mechanics  of  taxis 
must  be  deferred  to  the  general  treatment  of  the  subject  in 
Chapter  IX. 

SUMMARY  OF  THE  CHAPTER 

We  attempted  in  the  first  section  to  bring  together  observa- 
tions relating  to  the  action  of  various  chemical  substances  upon 
protoplasm  with  the  aims  of  discovering  the  general  laws  of 
poison-action  on  protoplasm  and  of  gaining  an  insight  into  the 
chemical  structure  of  protoplasm  and  the  chemical  operations 
involved  in  the  elementary  vital  processes.  We  ought  now, 
therefore,  to  attempt  to  draw  such  conclusions  as  the  imperfect 
and  often  confusing  data  we  have  collected  will  permit. 


46        CHEMICAL  AGENTS  AND  PROTOPLASM      [Cn.  I 

All  the  reagents  with  which  we  have  dealt  have  been  sub- 
stances capable  of  absorption  by,  mixture  with,  or  solution 
in,  water;  and  the  reason  for  this  is  that  almost  all  proto- 
plasm is  itself  enveloped  by  water  and  largely  composed  of 
water. 

For  the  most  part  we  have  dealt  with  mixtures  or  solutions. 
Now  the  action  of  these  is  a  double  one.  They  exhibit,  first, 
an  osmotic  action,  and,  secondly,  they  may  attack  the  molecules 
of  the  protoplasm,  transforming  them.  The  osmotic  action  we 
will  consider  in  the  third  chapter ;  the  transforming  one  alone 
concerns  us  now.  It  is  not  easy,  without  experiment,  to  say 
to  which  of  these  two  categories  of  action  the  change  wrought 
by  any  substance  is  due.  To  determine  between  the  two 
possible  causes  it  would  be  desirable  in  each  case  to  treat  the 
protoplasm  to  a  control  solution  having  the  same  osmotic  action 
as  the  first,  but  no  transforming  effect.  If  such  a  solution 
produces  no  modification  of  the  protoplasm,  then  the  effect 
wrought  by  the  first  reagent  is  due  purely  to  molecular  trans- 
formations. It  is  not  easy  to  find  a  reagent  of  which  we  may 
be  certain  that  it  acts  only  osmotically.  NaCl  is  probably  more 
generally  useful  in  this  way  than  any  other  substance.  In  the 
experiments  which  have  hitherto  been  made,  this  double  action 
of  solutions  has  not  been  sufficiently  considered.  Hence,  a 
doubt  concerning  the  immediate  cause  hangs  about  many  of 
the  phenomena  described  in  the  first  section. 

The  first  principle  which  the  data  collected  establish  is 
that  the  protoplasm  of  different  organisms  is  dissimilar.  This 
is  shown  by  the  diversity  in  their  chemical  reactions ;  by  the 
fact  that  whereas,  in  one  case,  a  'certain  percent  solution 
causes  so  extensive  a  molecular  transformation  as  to  result  in 
death,  in  another,  no  injurious  effect  is  produced. 

Thus,  according  to  BOER  ('90,  p.  479),  it  takes  of  gold 
chloride  to  kill  — 

TABLE   V 

Anthrax  bacillus 0.0125% 

Cholera  spirillum 0.1% 

Diphtheria  bacillus 0.1% 

Typhoid  bacillus 0.2% 

Glanders  bacillus 0.25% 


SUMMARY  OF  THE   CHAPTER  47 

Thus  the  weak  solution,  0.0125%,  of  AuCl3,  which  is  fatal  to 
anthrax,  does  not  injure  the  glanders  bacillus,  which  requires 
a  solution  20  times  as  strong ;  and  we  conclude  that  the  chemi- 
cal constitution  of  the  glanders  bacillus  must  be  different  from 
that  of  anthrax. 

The  dissimilarity  of  the  different  protoplasms  may  be  either 
a  qualitative  or  a  quantitative  one.  That  is  to  say,  the  kinds 
of  molecules,  or  the  proportions  of  the  different  molecules,  may 
differ  in  the  two  cases.  If  we  assume  that  gold  chloride  acts 
upon  protoplasm  by  the  Au  replacing  some  of  the  H  in  an 
amido-acid,  then  the  diversity  in  action  of  AuCl3  upon  anthrax 
and  typhoid  may  be  accounted  for  by  assuming  that  the  amido- 
acids  are  dissimilar  in  anthrax  and  typhoid  or  that  the  propor- 
tion of  the  kinds  especially  affected  is  different  in  the  two  cases. 
To  which  of  these  two  causes  the  diverse  reactions  to  AuCl3  are 
due  cannot  yet,  in  any  given  case,  be  determined. 

A  second  principle  which  we  may  draw  from  our  data  is  this : 
Some  kinds  of  protoplasm  have  a  general  high  resistance  to  all 
chemical  agents,  while  other  kinds  have  a  high  or  low  resistance 
to  particular  agents  only  (specific  high  or  low  resistance). 
Thus,  in  the  case  of  pathogenic  bacteria,  the  experiments  of 
BOER  ('90)  show  that,  in  general,  the  anthrax  bacillus  has  a 
low  resistance,  and  glanders  a  high  one.  His  experiments  were 
made  with  10  reagents  upon  five  kinds  of  bacteria.  Table  VII 
gives  in  modified  form  the  results  obtained  by  BOER.  His 
results  are  given  in  the  form  of  Table  V;  the  present  table 
is  constructed  from  the  original  by  making  the  mean  of  the 
five  observations  in  each  column  unity  and  reducing  the  sepa- 
rate observations  proportionately.  Thus  Table  V  becomes  — 

TABLE  VI 

Anthrax  bacillus 0.09 

Cholera  spirillum 0.75 

Diphtheria  bacillus 0.75 

Typhoid  bacillus 1.51 

Glanders  bacillus 1.88 

All  the  other  determinations  have  been  treated  in  like  manner. 
Throughout  the  table  the  numbers  in  each  column  stand  for 


48 


CHEMICAL  AGENTS  AND  PROTOPLASM 


[CH.  I 


relative  resistance  capacity.     The  reagents  are  placed  with  the 
weakest-acting  first. 

TABLE  VII 


CAUSTIC 

CARBOLIC 

MURIATIC 

SULPHURIC 

METHYL 

SUBSTANCES. 

SODA 

ACID 

ACID 

ACID 

VIOLET. 

(NaHO). 

(C6H60). 

(HC1). 

(H2S04). 

MOLECULAR  WEIGHTS. 

40 

94 

37 

98 

Anthrax  bacillus  .... 

0.46 

0.95 

0.40 

0.37 

0.07 

Cholera  spirillum    .  .  . 

1.38 

0.71 

0.32 

0.37 

0.33 

Diphtheria  bacillus    .  . 

0.69 

0.95 

0.63 

.  0.94 

0.17 

Typhoid  bacillus  .... 

1.09 

1.43 

1.46 

0.94 

2.22 

Glanders  bacillus  .... 

1.38 

0.95 

2.19 

2.36 

2.22 

SILVER 

GOLD 

MALACHITE 

OXTCYANIDE 

SUBSTANCES. 

NITRATE 

CHLORIDE 

GREEN. 

OP   Hg. 

AVERAGE. 

(AgNOg). 

(AuCl,). 

MOLECULAR  "WEIGHTS. 

170 

304 

Anthrax  bacillus  .... 

0.20 

0.09 

0.02 

0.93 

0.388 

Cholera  spirillum    .  .  . 

1.04 

0.75 

0.17 

0.62 

0.632 

Diphtheria  bacillus    .  . 

1.67 

0.75 

0.11 

0.93 

0.760 

Typhoid  bacillus  .... 

1.04 

1.51 

1.75 

1.25 

1.415 

Glanders  bacillus  .... 

1.04 

1.88 

2.92 

1.25 

1.802 

From  this  table  we  see  that  the  bacillus  of  glanders  is  more 
resistant  than  that  of  anthrax  (except  in  one  instance,  in  which 
the  resistance  is  equal  in  the  two  .cases)  whatsoever  be  the 
poison  employed.  The  bacillus  of  glanders  affords,  thus,  a 
good  illustration  of  an  organism  with  a  general  high  resistance 
capacity. 

The  diversity  in  general  resistance  capacity  which  is  found 
among  bacteria  exists  also  among  other  organisms.  Thus,  the 
parasitic  Ascaris  has  shown  itself  highly  resistant  in  all  cases 
in  which  the  action  of  a  poison  on  it  has  been  compared  with 
that  on  another  species;  for  instance  (p.  10)  0.1%  chloral 
hydrate  kills  Infusoria,  Rotifera,  and  diatoms  in  24  hours,  but 
•Ascaris  withstands  this  solution.  Again,  while  0.1%  HCN 
kills  Infusoria  quickly,  Ascaris  resists  3%  for  75  minutes.  The 
general  higher  resistance  may  be  due  to  one  of  three  causes : 


- 


SUMMARY  OF   THE   CHAPTER  49 


ther  to  the  fact  that  the  protoplasm  is  protected  from  attack, 
as  is  the  case  with  the  encysted  forms  of  Protozoa,  which  are 
very  resistant ;  or  to  the  fact  that  the  protoplasm  is  not  so 
readily  acted  upon  by  reagents  brought  actually  in  contact 
with  it,  clue  to  diminished  amount  of  water  or  other  structural 
modifications ;  or,  finally,  that  the  protoplasm  has  a  different 
composition,  certain  unstable  molecules  found  in  other  kinds 
of  protoplasm  being  absent. 

We  will  now  consider  the  phenomena  of  diversity  in  specific 
resistance  of  protoplasm.  A  case  of  specific  low  resistance  is 
found  in  the  nervous  tissue.  Thus  many  of  the  alkaloids,  e.g. 
nicotine  and  cocaine,  are  almost  indifferent  to  the  protoplasm 
of  Protista,  but  act  towards  the  nervous  system  as  powerful 
poisons.  Hence  we  are  led  to  conclude  that  nervous  protoplasm 
contains  especially  unstable  compounds,  upon  which  its  action 
depends.  When  they  are  subjected  to  the  action  of  very  weak 
—  towards  most  substances,  indifferent  —  reagents,  extensive 
and  fatal  transformations  occur. 

Cases  of  specific  high  resistance  are  apparently  found  in  some 
glands  which  secrete  intense  poisons,  or  in  some  organisms 
which  live  in  solutions  of  some  usually  poisonous  agent.  Ex- 
amples of  this  class  are  the  HCl-secreting  glands  of  the 
Vertebrate  alimentary  tract,  the  poison-glands  of  venomous 
serpents,  and  the  H2SO4-secreting  glands  of  Gasteropoda; 
also  the  vinegar  eel,  which  lives  in  4%  acetic  acid.  It  ought 
to  be  said  that  it  is  largely  an  inference  based  upon  experi- 
ments on  acclimatization,  that  these  glands  or  organisms  will 
not  show  a  general  high  resistance.  Experiments  are  needed 
to  determine  this  point.  As  to  the  cause  of  specific  high  resist- 
ance, I  believe  that  much  light  is  gained  from  the  facts  of 
acclimatization,  and  that  any  sufficient  theory  of  the  latter 
would  serve  also  to  explain  the  former  (see  p.  30). 

Under  the  general  poisons  we  have  distinguished  four  main 
groups  :  a.  oxidizing  poisons ;  b.  salt-forming  poisons ;  c.  sub- 
stitution poisons  ;  d.  catalytic  poisons.  I  will  comment  briefly 
upon  the  action  of  the  poisons  of  each  of  these  groups. 

a.  Oxidizing  Poisons.  —  The  ordinary  oxidation  processes  in 
[living  protoplasm  involve  the  consumption  not  of  the  proto- 


50        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

plasm  itself,  but  of  the  thermogenic  substances  stored  therein 
(sugar,  yolk).  After  these  have  been  consumed  in  starvation, 
or  when  the  organism  is  subjected  to  the  action  of  oxidizing 
poisons,  the  molecules  of  the  protoplasm  become  oxidized. 
All  protoplasm  which  is  readily  accessible  must  be  injured  by 
the  direct  attacks  of  "  active  "  oxygen. 

b.  Salt-forming  Poisons.  —  The  facility  with  which  an  acid 
or  a  base  forms  salts  with  the  protein  substances  of  the  proto- 
plasm must  depend,  in  large  part,  upon  the  quality  of   the 
protein  molecules.     It  is  well  known  that  certain  protein  sub- 
stances, such  as  keratin,  chitin,  and  fibrin,  are  not  readily  acted 
on  by  acids  or  bases,  and  it  seems  necessary  to  suppose  that 
some  such  resistant  proteids  are  the  essential  parts  of  glands 
which  secrete  these  reagents.     Into  this  group  fall  the  salts  of 
heavy  metals  characterized  by  their  extraordinary  fatalness. 

c.  Substitution  Poisons.  —  This   group   comprises,  besides  a 
few  sulphur   compounds,  almost  exclusively  nitrogenous  sub- 
stances, and   among   these   a   large  proportion  of   compounds 
with  closed  chains.     As  many  of  these  are  indifferent  to  dead 
albumen,  but  violent  poisons  to  living  protoplasm,  it  is  clear 
that  the  latter  must  contain  certain  extremely  unstable  groups 
(amido-,  aldehyde-,  and  keton-groups,    LOEW,    '80).     Among 
these   poisons   the   relation  between   molecular  structure  and 
poisonous  action  is  very  marked,  especially  in  the  nitro-com- 
pounds.     Thus,  bodies  containing  H  united  with  N  are  poison- 
ous in  direct  proportion  to  the  number  of  H  atoms  so  combined. 
It  seems  probable  that  H  so  combined  is  very  easily  given  up 
to  the  molecules  of   the   living   substance,   destroying   them. 
H  in  the  hydroxyl  radical  seems  also  more  easily  parted  with 
than  H  joined  to  C. 

d.  Catalytic  Poisons.  —  Chiefly  organic  compounds    of   the 
fat  series,  which  have  little  chemical  energy  and  produce,  for 
the  most  part,  anaesthesia.     The  poisonous  action  seems  here 
proportional  to  the  complexity  and  instability  of  the  compound. 
Thus,  in  many  groups,  when  the  alkyls  CH3  — ,  C2H5  — ,  etc., 
are  successively  introduced,  the  substance  grows  more  poison- 
ous as  the  number  of  atoms  in  the  alkyl  increases.     In  the 
methan  series  and  among  sulphureted  compounds  the  substi- 
tution of  Cl  for  H  increases  the  poisonous  action. 


TJ 
SUMMARY  OF   THE   CHAPTER 


(The  study  of  the  action  of  poisons  upon  protoplasm  gives  us 
insight  into  the  extreme  complexity  of  the  living  substance 
its  composition  out  of  numerous  kinds  of  compounds,  many 
which  are  extremely  unstable.  Not  all  protoplasm  contains 
the  same  compounds,  hence  it  must  be  a  very  dissimilar  thing 
in  different  organisms.  Not  all  of  the  compounds  in  any  pro- 
toplasmic body  are  essential  to  life,  for  we  may  act  upon  a 
protoplasmic  body  by  a  weak  reagent,  and  gradually  change 
its  composition  so  that  it  will  no  longer  be  killed  by  the  strong 
solution,  and  all  of  this  without  perceptible  injury  —  at  least, 
this  is  the  conclusion  to  which  the  study  of  acclimatization  of 
Protista  leads  us.  The  altered  chemical  constitution  will  be 
transmitted  in  the  division  of  the  individual,  and  thus  the 
composition  of  the  protoplasm  of  a  race  will  have  been  deter- 
mined by  the  medium  in  which  it  and  its  ancestors  have  been 
living. 

Finally,  we  may  consider  what  light  the  action  of  reagents 
throws  upon  the  processes  involved  in  the  elementary  vital 
functions.  The  normal  movement  of  protoplasm  is  profoundly 
modified  by  interfering  with  the  oxygen  supply.  Thus,  when 
the  oxygen  pressure  is  diminished,  movements  are  retarded  ;  in 
the  presence  of  pure  oxygen  they  are  accelerated.  Some  anaes- 
thetic or  paralyzing  agents  —  e.g.  chloroform  and  some  alka- 
loids, veratrin,  atropin,  cocaine,  strychnin,  and  antipyrin — give 
rise  first  to  acceleration,  then  to  disappearance  of  movements 
in  the  protoplasm.  Protoplasmic  movement  is,  consequently, 
closely  associated  with  oxidation,  and  it  does  not  occur  in  the 
absence  of  irritability. 

Normal  locomotion  is  interfered  with  by  strychnin  and  co- 
caine. Their  stimulating  action  produces  accelerated  move- 
ments, and  these  are  accompanied  by  loss  of  coordination. 

Since  many  catalytic  poisons  (anaesthetics)  destroy  irrita- 
bility, one  may  conclude  from  the  action  of  these  chemical 
agents  that  (p.  7)  stability  of  molecular  movement  is  essential 
to  the  performance  of  this  function. 

Disturbance  of  the  excretory  function  results  from  the  action 
of  CO,  NH3,  chloroform,  cocaine,  strychnin ;  at  least,  an  ex- 
cessive vacuolation  of  the  protoplasmic  body  occurs  under  the 
action  of  these  agents. 


52        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

Experiments  on  chemotaxis  show  that  many  substances 
brought  near  to  protoplasmic  bodies  control  their  locomotion. 
The  effect  upon  locomotion  depends  both  upon  the  kind  of 
protoplasm  and  the  strength  of  the  reagent.  In  many  cases, 
a  certain  strength  of  reagent  attracts  an  organism,  while  a 
stronger  solution  repels,  and  a  weaker  solution  is  indifferent. 
In  such  a  case  we  may  speak  of  the  protoplasm  as  being  attuned 
to  the  attracting  strength  of  the  reagent.  We  find  great  diver- 
sity in  the  strength  of  solution  of  a  reagent  to  which  different 
protoplasms  are  attuned.  This  difference  of  attunement  to 
chemotactic  reagents  is  parallel  to  the  difference  in  strength  of 
the  killing  solution  of  various  protoplasms.  As  the  latter  is 
probably  due  to  the  past  action  of  chemical  agents  upon  the 
protoplasm,  so  is  also  the  former. 


APPENDIX   TO    CHAPTER  I 

Cytotaxis  (=  Cytotropisvi) 

Roux  ('94)  has  given  the  latter  name  to  a  phenomenon  which 
is  probably  only  a  special  case  of  chemotaxis,  but  which  may  be 
better  considered  apart.  He  isolated,  in  an  indifferent  medium, 
two  or  three  cells  from  the  egg  of  a  frog  (Raiia  fusca)  at  the 
morula  or  blastula  stage  of  development.  These  he  placed  near 
each  other  upon  a  glass  slide,  and  found  that  they  moved  slowly, 
and  that  the  direction  of  the  movement  of  any  one  cell  was, 
under  certain  conditions,  determined  by  the  position  of  the 
other  cell  or  cells. 

In  order  to  perform  the  experiment  a  proper  medium  in  which  to  study 
the  movement  of  the  cells  must  be  prepared  as  follows:  a  small  quantity  — 
5  to  10  ccm.  —  of  fresh  egg  albumen  (not  cut  up,  but  with  the  albumen 
threads  intact)  is  filtered  through  clean  wadding,  and  the  completely  clear 
filtrate  is  used.  In  other  cases  a  more  or  less  strong  salt  solution  is 
employed.  The  cleavage  cells  are  isolated  in  the  filtrated  albumen,  on  a 
glass  plate,  by  means  of  needles.  To  diminish  evaporation  the  glass  plate 
is  put  into  a  shallow  glass  vessel  containing  several  drops  of  water. 

When  two  cells  were  placed  near  each  other  (about  one-fourth 
of  their  diameter  apart),  the  distance  between  them  diminished. 
The  approach  took  place  along  a  line  joining  the  two  cells  ; 


APPENDIX,—  CYTOTAXIS 


53 


and  when  several  pairs  of  cells  were  in  the  field,  this  movement 
took  place  in  various  directions,  indicating  that  their  move- 
ment was  not  determined  by  conditions  outside  the  approaching 
cells.  To  get  further  light  on  the  migration  of  the  cells,  their 
distance  apart  was  meas- 
ured at  short  intervals 
of  time.  The  results  of 
two  series  of  such  meas- 
urements are  represented 
graphically  in  Figs.  6  and 
7.  In  both  of  these  dia- 
grams the  heavy  lines 
indicate  the  successive 
positions  assumed  by 
four  points ;  namely,  the 
points  of  the  two  cells 
which  are  nearest  each 
other  and  those  which 
are  most  distant.  In 
the  first  case  the  cells 
traverse  the  distance  of 
their  diameters  (58  //,) 
in  about  10.5  minutes. 
The  rate  of  migration 
is,  however,  extremely 
variable.  In  some  cases 
the  cells  seem  even  to 
move  apart  (negative 
cytotaxis  ?) . 

Certain  special  cases 
are  worthy  of  considera- 
tion. When  a  third  cell 
lies  near  an  approaching 
pair,  the  path  of  migra- 
tion of  the  pair  may  become  convex  towards  the  third  cell. 
Two  cell-complexes,  each  composed  of  three  or  four  cells, 
may  approach  and  connect.  But  masses  composed  of  a 
larger  number  of  cells  form  "  closed  complexes  "  which 
show  no  cytotactic  activity.  The  isolated  cells  of  differ- 


FIGS.  6,  7. — Two  sets  of  curves,  showing  the 
course  of  "cytotactic"  movements  of  the 
cleavage  cells  of  the  frog.  In  each  figure 
the  dotted  line  represents  a  diameter  of  the 
cell.  The  full  line  represents  the  successive 
positions  of  the  extremities  of  the  diameters 
as  the  cells  approach.  The  distances  between 
horizontal  lines  =  4/n ;  between  vertical  lines, 
75  seconds.  (From  Roux,  '94.) 


54        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

ent   eggs    of   the    same    species    behave    like    cells    from    the 
same  egg* 

By  these  important  experiments  it  is  established  that,  inside 
of  the  body,  parts  may  act  upon  parts,  determining  the  direc- 
tion of  motion.  The  importance  of  this  fact  will  be  discussed 
in  a  later  Part  of  this  book. 


LITERATURE 

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ADERHOLD,  R.  '88.     Beitrag  zur  Kenntnis  richtender  Krafte  bei  der  Bewe- 

gung  niederer  Organismen.     Jena.  Zeitschr.     XXII,  310-342. 
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maux  et  aux  vegetaux.     Tome  I,  404  pp.     Paris. 
BOER,  O.  '90.     Ueber  die  Leistungsfahigkeit  mehrerer  chemischer  Desin- 

fectionsmittel  bei  einiger  fiir  den  Menschen  pathogenen   Bacterien. 

Zeitschr.  f.  Hygiene.     IX,  479-491. 
BOSCH,  C.  TEN  '80.     De  physiologische  werking  van  chinamine.     Onder- 

zoek.  Physiol.  Lab.  Utrecht.     V,  248-292. 
BINZ,  C.  '67.     Ueber  die  Einwirkung  des  Chinin  auf  Protoplasma-Bewe- 

gungen.     Arch.  f.  mik.  Anat.     Ill,  383-389. 
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Standpunkt  betrachtet.     Arch.  f.  exper.  Path.  u.  Pharm.     XI,  200- 

230. 
BOKORNY,  T.  '86.     Das  Wasserstoffsuperoxyd  und  die  Silberabscheidung 

durch  actives  Albumin.     Jahrb.  f.  wiss.  Bot.     XVII,  347-358. 
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Jahrb.  f.  wiss.  Bot.    XIX,  206-220. 
'93.   Ueber  die  physiologische  Wirkung  der  tellurigen  Saure.     [Abstr.  in] 

Bot.  Centralbl.     LVII,  16. 
BOURNE,  A.  G.  '87.     The 'Reputed  Suicide  of  Scorpions.     Proc.  Roy.  Soc. 

London.     XLH,  17-22. 
BUCHNER,  H.  '91.     Die  chemische  Reizbarkeit  der  Leukocyten  und  deren 

Beziehung  zur  Entziindung  und  Eiterung.     Sb.  Ges.  Morph.  u.  Physiol. 

Miinchen.     VI,  148-152. 
'92.     Die  keimtodtende,  die  globulicide  und  die  antitoxische  Wirkung 

des  Blutserums.     Miinchener  Med.  Wochenschr.     XXXIX,  119-12:'.. 

CALMETTE,  A.  '94.     L'immunisation  artificielle  des  animaux  contre  le  venom 

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LITERATURE  55 

CHARPENTIER,  A.  '85.     Action  de  la  cocaine  et  d'autres  alcalo'ides  sur  cer- 
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184. 
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Pressure.     Proc.  Roy.  Soc.  Lond.     XL VI,  370,  371.     June  20,  1889. 
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Centralbl.     LVII,  3-6. 
DANILEWSKI,  B.  '92.     Ueber  die  physiologische  Wirkung  des  Cocains  auf 

wirbellose  Thiere.     Arch.  f.  d.  ges.  Physiol.     LI,  446-454. 
DAREMBERG,  G.  '91.     Sur  le  pouvoir  destructeur  du  serum  sanguin  pour  les 

globules  rouges.     C.  R.  Soc.  Biol.    XLIII,  719-721. 

DARWIN,  C.  '75.    Insectivorous  Plants.    462  pp.    New  York :  Appleton  &  Co. 
DAVENPORT,   C.  B.   and  NEAL,  H.  V.,  '96.    On  the  Acclimatization  of 

Organisms  to  Poisonous  Chemical  Substances.     Arch,  f .  Entwick.  d. 

Organismen.     II,  564-583.     28  Jan.  1896. 
DEMOOR,  J.  '94.     Contribution  a  1'etude  de  la  physiologic  de  la  cellule  (in- 

dependance  functionnelle   du  protoplasma  et  du  noyau).      Arch,  de 

Biol.     Xin,  163-244,  Pis.  IX,  X.    28  Feb.  1894. 
DEWITZ,  J.  '85.     Ueber  die  Vereinigung  der  Spermatozoen  mit  dem  Ei. 

Arch.  f.  d.  ges.  Physiol.     XXXVII,  219-223.     29  Oct.  1885. 
EHRLICH,  P.  '91.    Experimentelle  Untersuchungen  iiber  Immunitat.    I  Ueber 

Ricin.     II  Ueber  Abrin.  Deutsche  med.  Wochenschr.     976-979 ;  1218, 

1219. 
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Pflanzen.     Ofversigt  af  Finska  Vetensk.  Soc.  Forh.     XXVIII,  36-53. 
ENGELMANN.    T.  W.   '81.     Neue   Methode   zur   Untersuchung   der   Sauer- 

stoffauscheidung  pflanzlicher  und  thierischer  Organismen.     Arch.  f. 

d.  ges.  Physiol.     XXV,  285-292.     20  June,  1881. 
'82.     Ueber  Licht-  und  Farbenperceptiou  niederster  Organismen.     Arch. 

f.  d.  ges.  Physiol.     XXIX,  387-400.     3  Nov.  1882. 
'94.     L'emission  d'oxygene  sous  I'mfluence  de  la  lumiere,  par  les  cellules 

a  chromophylle,  demontree   au   moyen   de  la  methode  bacterienne. 

Arch.  Neerland.     XXVHI,  358-371. 
FAYRER,  J.  '74.     The  Thanatophidia.     2d  ed.,  178  pp.,  31  pis.     London : 

Churchill. 
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und  Reaktionen   thierischer  und  pflanzlicher  Zellen.  Jena.  Zeitschr. 

XVII,  1-349.     Taf.  I-TII.     19  Jan.  1884. 
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Jour,  of  Physiol.     XI,  573-605.     Dec.  1890. 
HEIDENSCHILD,  W.  '86.     Untersuchungen  iiber  die  Wirkung  des  Giftes  der 

Brillen-  und  der  Klapperschlange.     Jahresber.  d.  Thier-Chem.     XVII, 

330.     [From  Inaug.  Diss.  Dorpat.     Lookmann,  1886.] 
HERTWIG,  O.  and  R.  '87.     Ueber  den  Befruchtungs-  und  Teilungsvorgang 

des  tierischen   Eies  unter  dem  Einfluss   ausserer   Agentien.      Jena. 

Zeitschr.     XX,  120-241.     8  Jan.  1887. 


56        CHEMICAL  AGENTS  AND  PROTOPLASM     [Cn.  I 

HOFER,  B.  '90.     Ueber  die  lahmende  Wirkung  des  Hydroxylamins  auf  die 

contractilen  Elements.     Zeitschr.  f.  wiss.   Mikr.     VII,  318-326.     18 

Dec.  1890. 
KANTHACK,  A.  A.  '92.     The  Nature  of  Cobra  Poison.     Jour,  of  Physiol. 

XIII,  272-299.     May,  1892. 
KRUKENBERG,  C.  F.  W.  '80.     Vergleichend-physiologische  Studien.     1  Reihe, 

1  Abth.,  77-155. 
KUHNE,  W.  '64.     Untersuchungen  liber  das  Protoplasma  und  die  Contrac- 

tilitat.     158  pp.,  8  Taf .     Leipzig :  Engelmann. 
LEBER,  T.  '88.     Ueber  die  Entstehung  der  Entziindung  und  die  Wirkung 

der  entziindungserregenden  Schadlichkeiten.     Fortschritte  d.  Medicin. 

VI,  460-464. 

LOCKE,  F.  S.  '95.    On  a  Supposed  Action  of  Distilled  Water  as  such  on  Cer- 
tain Animal  Organisms.     Jour,  of  Physiol.     XVIII,  319-331.     5  Sept. 

1895. 
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mit  dem  Heliotropismus  der  Pflanzen.     118  pp.     Wiirzburg :  Hertz. 
LOEW,  O.  '77.     Lieutenant  Wheeler's  Expedition  durch  das  siidliche  Cali- 

fornien  im  Jahre  1875.     Petermann's  Geogr.  Mitth.     XXIII,  134-140. 
'83.     Sind  Arsenverbindungen  Gift  f iir  pflanzliches  Protoplasma  ?    Arch. 

f.  d.  ges.  Physiol.     XXXII,  111-113.     12  Sept.  1883. 
'85.     Ueber  den  verschiedenen  Resistenzgrad  im  Protoplasma.      Arch. 

f.  d.  ges.  Physiol.     XXXV,  509-516.     30  Jan.  1885. 
85a.     Ueber  die  Giftwirkung  des  Hydroxylamins  verglichen  mit  der  von 

anderen  Substanzen.      Arch.  f.  d.  ges.  Physiol.      XXXV,  516-527. 

30  Jan.  1885. 
'87.      Ueber    Giftwirkung.      Arch.  f.   d.  ges.  Physiol.     XL,   437-447. 

18  May,  1887. 
'88.     Physiologische  Notizen  iiber  Formaldehyd.      Sb.  Ges.  f.  Morpol.  u. 

Physiol.  Miinchen.     IV,  39-41. 
'91.     Die  chemischen  Verhaltnisse  des  Bakterienlebens.      Centralbl.  f. 

Bakteriol.  u.  Parasitenk.     IX,  659-663 ;  690-697 ;  722-726 ;  757-760  ; 

789-790.     May-June,  1891. 
'92.     Ueber  die   Giftwirkung    des    Fluornatriums    auf    Pflanzenzellen. 

Miinchen er  Med.  Wochenschr.     XXXIX,  587. 
'93.     Ein  naturliches  System  der  Gif t-Wirkungen .     136  pp.      Miinchen, 

Wolff  u.  Liineburg,  1893. 
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stark  verdiinnter  alkalischer  Silberlosung.     Bot.  Centralbl.     XXXIX, 

369-373 ;  XL,  161-164,  193-197. 
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448  pp.     5  pis.     New  York  :  Appleton. 
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IX,  533-574. 
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LITERATURE  57 


CHAPTER  II 

EFFECT  OF  VARYING  MOISTURE    UPON  PROTOPLASM 

IN  this  chapter  it  is  proposed  to  speak  (I)  of  the  amount  of 
water  in  organisms ;  (II)  of  the  effect  of  desiccation  upon  the 
functions  of  protoplasm ;  (III)  of  the  acclimatization  of  organ- 
isms to  desiccation,  and  (IV)  of  the  control  of  the  direction 
of  locomotion  by  moisture  —  hydrotaxis. 


§  1.   ON  THE  AMOUNT  OF  WATER  IN  ORGANISMS 

Any  theory  of  the  structure  of  protoplasm  must  recognize 
that  water  forms  the  greater  part  of  the  whole  mass ;  between 
60%  and  90%.  In  the  case  of  dry  seeds  and  grains,  however,  it 
may  fall  below  15%.  Many  determinations  have  been  made  of 
the  proportion  of  water  in  the  body  of  entire  organisms  and  in 
their  organs.  I  give  in  tabular  form  some  of  these  determina- 
tions, which  were  made  by  BEZOLD  ('57),  designated  by  (B) ; 
KRUKENBERG  ('80),  designated  by  (K);  and  LIEBERMANN 
('88),  designated  by  (L). 

TABLE   VIII 


SPECIES. 


CONDITIONS  OF  WEIGHING. 


%  WATJSU. 


Various  sponges  (K) 


Medusa :  Rhizostoma  Cuvieri  (K) . 
Various  Actinia  (K) 


Alcyonium  palmatum  (K)  .... 
Asteracanthion  glacialis  (K).  .  . 
Lumbricus  complanatus  (K) .  .  . 


In  most  cases,  kept  a  short  time  in 
fresh  sea  water ;  dried  on  surface 
and  weighed. 

Whole  animal,  directly  from  water 

Piece  of  disc. 

A  few  minutes  after  removal  from 
sea. 

A  little  water  lost  from  central  cavity 

Weighed  when  fresh,  73.5  g. 

Weighed  850  g. 

2  large  specimens 

58 


84.0  to 
74.5 
95.4 
95.0 

87.7  to 

83.2 

84.3 

82.3 

87.8 


>]        DESICCATION  AND  PROTOPLASMIC   FUNCTIONS          59 


SPECIES. 

CONDITIONS  OP  "WEIGHING. 

%  WATEE. 

Oniscus  murarius  (B)    

200  young  individuals 

68.1 

1  individual 

81.9 

3  individuals  weighing  from  16.6  to 

Doris  tuberculata  (K) 

27.4  g. 

71.1 

88.4 

3  individuals 

86.5 

6  individuals  weighing  from  4.3  to 

Lininx  maximus  (B)          

27.1  g. 
4  individuals  weighing  from  0.1  to 

86.8 

Botryllus  (K)      

17.1  g. 
4  individuals  weighing  from  111.2 

82.1 

Various  Vertebrates  (B) 

to  35.2  g. 

93.6 
58.4  to 

Chick  (L)       

80.1 

7  days  old                        

Embryo  only,  yolk  removed 

92.8 

21  days  old  

Embryo  only,  ready  to  hatch 

80.4 

Turnip  (root)                     

From  Goodale's  Physiolog.  Bot.,  p. 

236 

91.0 

These  determinations  suffice  to  show  that  water  immensely 
predominates  over  any  other  substance  in  active  organisms, 
and  indicate  that  it  plays  an  important  role. 

The  role  played  by  water  is,  in  fact,  extremely  varied.  It 
serves  to  maintain  that  unstable,  foam-like  structure  of  the 
protoplasm  upon  which  its  capacity  for  movement  depends ;  it 
acts  as  a  solvent  for  matter  taken  into  the  protoplasmic  body; 
and  it  serves  to  transport  dissolved  substances  from  place  to 
place  in  the  organism.  In  a  word,  it  is  essential  to  movement 
and  to  those  chemical  processes  which  constitute  metabolism. 


§  2.    Ox   THE   EFFECT  OF   DESICCATION  UPON  THE   FUNC- 
TIONS OF  PROTOPLASM 

We  may  consider  this  topic  under  the  following  heads  : 
(1)  effect  upon  metabolism ;  (2)  effect  upon  the  motion  of 
protoplasm;  and  (3)  the  production  of  desiccation-rigor  and 
death. 

1.  Effect  of  Dryness  on  Metabolism.  —  Since  water  is  so 
essential  to  metabolism,  we  should  expect  that  a  diminution  of 
metabolism  would  accompany  dryness.  And  this  is  clearly  the 
case.  Thus  dry  seeds,  in  which  the  water  is  reduced  to  only  10 


60  MOISTURE  AND  PROTOPLASM  [Cn.  II 

to  15%,  when  placed  under  conditions  of  temperature  favor- 
able to  metabolism,  show  almost  no  change  in  the  course  of 
days.  This  has  been  indicated  also  by  an  experiment  of 
KOCHS'  ('90,  p.  685),  who  placed  seeds,  which  had  been  dried 
in  a  vacuum,  in  a  receptacle  connected  with  a  GEISSLER'S  tube, 
such  as  is  used  in  the  spectroscopic  study  of  gases.  The  air 
was  completely  pumped  out  of  both  vessels,  and  after  some 
months  a  spectroscopic  study  of  the  gases  in  the  GEISSLER'S 
tube  showed  no  trace  of  nitrogen  or  carbon,  yet  the  seeds  later 
germinated.  This  experiment  can  hardly  be  considered  to 
demonstrate  KOCHS'  point,  however,  since  the  seeds  were 
deprived  of  oxygen,  as  well  as  moisture. 

The  act  of  drying  may,  on  the  contrary,  induce  the  manu- 
facture and  elimination  of  certain  secretions.  This  occurs 
apparently  in  many  Protista,  which  form  cysts  in  the  drying 
pools.  This  phenomenon  is  seen  again  in  some  of  the  higher 
animals,  —  such  as  our  garden  slugs,  —  which  secrete  slime  in 
large  amount  when  kept  for  a  short  time  in  a  dry  place.  In 
both  cases  the  result  is  of  immense  importance  for  the  con- 
tinued life  of  the  organism,  —  in  both  cases  it  is  to  be  consid- 
ered a  response  to  the  stimulus  afforded  by  evaporation  of  water. 

2.  Effect  of  Dryness  upon  the  Motion  of  Protoplasm.  —  We 
have  seen  that  water  plays  an  important  role  in  the  movement 
of  protoplasm.     When  by  any  means  the  water  is  partly  with- 
drawn, the  protoplasmic  currents  will  be  slowed.     When,  on 
the  contrary,  protoplasm,  which  is  lying  in  an  "  indifferent " 
medium,  such   as   blood   serum,  is  placed   in   distilled  water, 
unusually  active  movements  occur.     This  has  been  shown  by 
ENGELMANN  ('68,  p.  446)  in  the  case  of  the  spermatozoa  of  the 
frog,  and  the  ciliated  epithelium  of  the  frog's  oesophagus  just 
removed  from  its  body.     Similarly,  DEHNECKE  ('81)  found  that 
protoplasm  of  the  tissue  cells  of  the  higher  plants  exhibited 
abnormally  rapid  movements  upon  adding  water.     These  obser- 
vations indicate  that  water  may  act  as  a  stimulus  to  the  move- 
ment of  protoplasm. 

3.  Desiccation-rigor  and  Death.  —  It  is  a  familiar  fact  which 
has   been  established   by  over  a  hundred   and   fifty  years   of 
experimentation,  that  some  organisms,  when  gradually  dried, 
may   cease   from   movements.      This   immotile  condition    has 


§2]        DESICCATION  AND   PROTOPLASMIC   FUNCTIONS          61 

sometimes  been  regarded  as  death.  By  PREYER  ('91)  it  has 
been  called  "  anabiosis."  I  shall  call  it  desiccation-rigor,  and 
correlate  it  with  phenomena,  produced  by  various  other  agents, 
which  cause  the  cessation  of  a  movement  that  is  restored  again 
when  the  action  of  the  untoward  agent  is  withdrawn. 

And  these  are  just  the  conditions  we  meet  with  here,  —  ces- 
sation of  activity  without  loss  of  power  of  revival.  This  was 
very  evident  from  the  work  of  SPALLAXZAXI  (1787,  Tom.  II, 
pp.  212,  213).  This  author  showed  clearly  that  one  and  the  same 
adult  rotifer  can  be  observed  in  the  evaporating  drop,  until  all 
the  water  is  gone,  and  it  has  lost  all  movement  and  its  normal 
form.  If,  after  an  hour,  the  slide  is  moistened  again,  the 
rotifer  reassumes,  by  degrees,  its  natural  form  and  activities. 
SPALLAXZAXI  noticed,  what  has  been  the  nearly  unanimous 
testimony  of  subsequent  observers,  that  a  rotifer  dried  for 
hours  on  clean  glass  does  not  revive ;  revivification  occurs 
only  when  the  rotifers  have  crawled  into  sand.  As  for  the 
length  of  time  during  which  desiccation-rigor  may  persist 
in  rotifers  without  death  occurring,  we  know  only  that  it  may 
be  considerable,  extending  through  months,  and  even  years. 

Similar  phenomena  to  those  observed  in  rotifers  have  been 
described  for  tardigrades  and  certain  nematodes,  although  these 
organisms  have  not  been  studied  in  so  much  detail.  Among 
the  tardigrades  only  those  species  which  live  in  moss,  and 
are  thus  especially  liable  to  desiccation,  withstand  drying. 
(LAXCE,  '94.)  Among  nematodes,  Tylenchus  devastatrix, 
KUHX,  which  lives  in  grains  of  wheat,  is  a  classic  object  of 
study.  Strongylus  rufescens  is,  according  to  RAILLIET  ('92), 
capable  of  resisting  dry  ness  for  68  days  or  more.  We  may 
thus  conclude  that  adult  organisms  of  certain  species  may  be 
subjected  to  desiccating  influences,  and  that  those  same  indi- 
viduals may  resist  them  so  as  to  reexhibit  activities  after  the 
return  of  favorable  conditions.* 

While  the  results  of  these  drying  experiments  are  scarcely 
doubted,  much  difference  of  opinion  has  arisen  concerning  the 
interpretation  of  the  results.  The  first  moot  point  is  the 
degree  of  desiccation  which  the  protoplasm  of  the  organisms 

*  See  in  connection  with  this  the  valuable  report  of  BROCA  ('61). 


62  MOISTURE  AND  PROTOPLASM  [Cn.  II 

experiences.  Many  writers  have  assumed  that  this  has  been 
rendered  in  their  experiments  very  great  or  nearly  perfect. 
Thus  DOYERE  ('42,  p.  28)  says:  "What  is  the  condition  of 
the  animalcules  in  the  dried  sand  of  the  gutters?  I  have 
never  seen  them,  at  such  times,  in  any  other  condition  than 
reduced  to  spangles  as  fragile  and  more  deformed  than  when 
dried  free  on  the  glass.  I  have  never  discovered  a  single  one 
which  manifested  any  traces  whatever  of  life,  or  which  did  not 
present  all  the  appearances  of  a  complete  desiccation.  Never- 
theless, I  do  not  pretend  by  this  to  invalidate  all  contrary  asser- 
tions ;  the  principal  fact,  that  of  the  return  to  life  after  an 
absolute  desiccation,  is  not  affected  thereby."  The  physicist 
GAVARRET  ('59,  p.  317)  subjected,  for  34  days,  moss  contain- 
ing rotifers  to  a  vacuum  having  a  pressure  of  only  4  mm.  of 
mercury,  and  other  experimenters  have  likewise  employed  a 
similar  "chemically  drying"  device,  which  they  believed  capa- 
ble of  extracting  all  water  from  the  protoplasm. 

The  evidence  that  all  water  is  withdrawn  from  the  body  of 
the  organism  is  often  very  slight.  The  fact  that  the  seeds  or 
plant  tissues  in  which  nematodes  or  tardigrades  are  living, 
have  been  dried  until  they  lose  no  appreciable  weight,  is  not 
sufficient  evidence  that  their  inhabitants  are  completely  dried. 

On  the  other  hand,  there  is  positive  evidence  that  one,  at 
least,  of  the  organisms  which  has  been  considered  as  having 
been  absolutely  dried,  can  protect  itself  from  this  condition. 
It  is  especially  DAVIS  ('73)  who  has  shown  this.  This  author 
has  experimented  with  the  rotifer  Philodina  roseata.  When 
dried  on  a  glass  plate  with  sand,  it  assumes  a  spherical  form. 
At  the  same  time,  however,  it  secretes  a  gelatinous  envelope. 
Thus  encapsuled  it  may  rest  for  days  until  upon  the  addition 
of  water  it  reassumes  its  active,  adult  form.  That  a  layer 
of  such  gelatinous  substance  is  sufficient  to  resist  the  drying 
action  of  a  vacuum-chamber  with  sulphuric  acid,  was  illus- 
trated by  putting  grapes  varnished  with  gelatine  in  such  a  dry 
chamber  for  one  week.  They  emerged  in  a  fresh,  juicy  con- 
dition. -  One  of  the  encapsuled  rotifers  was  crushed  after 
"desiccation"  and  yielded  under  the  cover-glass  a  drop  of  fluid. 
In  this  case  then  the  rotifer  was  not  fully  dried.  DAVIS 
accounts  for  the  fact  that  isolated  rotifers  dried  on  a  clean 


§  2]        DESICCATION  AND   PROTOPLASMIC   FUNCTIONS          63 

slide  will  not  survive  desiccation,  on  the  ground  that  the  sand 
forms  a  necessary  retreat  in  which  the  organism  can  quietly 
encapsule  itself.  Of  the  fact  of  such  encapsuling  there  can  be 
no  doubt ;  it  is  abundantly  substantiated  by  the  testimony  of 
HUDSON  ('73  and  '86).  There  is  a  doubt,  however,  whether 
this  encapsuling  is  a  phenomenon  common  to  all  organisms 
which  can  resist  desiccating  influences,  and,  therefore,  whether 
DA  vis's  explanation  is  generally  applicable.  To  sum  up  :  I 
believe  there  is  no  sufficient  evidence  that  an  adult  organism 
or  active  protoplasm  of  any  sort  can  rapidly  lose  all  of  its  "  free 
water"  without  such  a  destruction  of  its  finer  structure  as 
would  make  it  incapable  of  exhibiting  vital  activities  upon 
moistening  again. 

A  much  greater  capacity  undoubtedly  inheres  in  spores  and 
seeds.  Thus  KOCHS  ('90)  subjected  perforated  seeds  of  Zea 
mais,  Phaseolus,  and  Triticum  vulgare  to  an  almost  perfect 
vacuum  (made  by  a  mercury  pump)  for  8  days,  and  they  nearly 
all  germinated.  Even  the  small  radish  seed,  with  part  of  the 
cuticula  removed,  subjected  to  a  vacuum  for  three  weeks  ger- 
minated perfectly.  Probably  there  is  no  limit  to  the  amount 
of  desiccation  which  seeds  and  other  masses  of  protoplasm 
especially  adapted  to  resist  desiccation  can  withstand. 

The  second  moot  point  is  this  :  Is  the  protoplasm,  rendered 
immotile  by  drying,  living  or  not  ?  SPALLANZANI  prejudiced 
the  question  by  the  title  of  his  chapter  on  this  matter, — 
"  Observations  and  experiments  on  some  marvellous  animals 
which  the  observer  can  at  his  will  make  pass  from  death  to 
life  "  ;  and  he  and  many  of  his  successors  argue  that  death  has 
truly  occurred.  PREYER  ('91),  however,  prefers  to  reserve  the 
term  "  dead "  for  protoplasm  which  is  at  the  same  time  lifeless 
and  incapable  of  life  ;  while  to  protoplasm  which  is  lifeless  but 
capable  of  revivification  he  applies  the  term  "  anabiotic."  The 
question  then  is  this,  is  life  truly  suspended  during  the  immo- 
tile state  ?  If  we  think  of  life  as  the  sum  of  the  chemical 
changes  occurring  in  the  protoplasm,  we  shall  realize  that  all 
degrees  of  vitality,  even  to  complete  cessation  of  activity,  may 
occur  without  our  being  able  anywhere  to  say  at  this  point  life 
becomes  extinct.  We  can  hardly  hope  ever  to  deny  that  mini- 
mum vital  changes  are  occurring ;  since  the  minimum  changes 


64  MOISTURE   AND   PROTOPLASM  [Cn.  II 

must  be  beyond  our  ken.  That  these  vital  changes  are  some- 
times exceedingly  slight,  is  sufficiently  indicated  by  the  experi- 
ments upon  seeds  performed  by  KOCHS  ('90),  and  referred  to 
on  p.  60.  That,  however,  slight  changes  are  occurring  even 
in  seeds  is  indicated  by  the  fact  that  dessication-rigor  cannot 
continue  indefinitely  without  loss  of  the  power  of  revivifi- 
cation. 

In  the  case  of  the  rotifers,  tardigrades,  and  nematodes,  months, 
and  even  years,  may  elapse  without  complete  loss  of  capacity 
for  revivification.  It  is  generally  admitted,  however,  that  in 
cases  of  long-continued  drought,  the  chances  of  revitalizing 
upon  moistening  are  much  diminished.*  In  the  case  of  seeds 
it  has  been  maintained  that  under  certain  conditions,  such  as 
are  realized  in  the  mummy-graves  of  Egypt,  life  may  persist 
for  more  than  a  thousand  years.  However,  the  experiments  of 
MUNTER  ('47),  and  more  especially  of  KOCHS  ('90,  p.  683), 
throw  doubt  upon  this  assertion,  since  they  found  that  the 
ancient,  charred  seeds  fell  to  pieces  in  water  like  lime.  As 
for  seeds  preserved  above  ground  in  the  ordinary  way,  KOCHS 
was  assured  by  seedmen  that  they  could  not  remain  capable 
of  germination  over  10  years.  These  facts  go  to  show  that 
gradual  changes  occur  in  the  dry  protoplasm  which  are  prob- 
ably metabolic  changes,  i.e.  vital  changes  ;  and  that  therefore 
life  is  hardly  extinct  in  the  very  dryest  protoplasm. 

The  whole  matter  of  desiccation-rigor  is,  after  all,  one  with 
which  we  are  familiar  in  nature's  larger  laboratory.  Many 
Protista,  when  the  ponds  in  which  they  live  dry  out,  encyst 
themselves  and  enter  into  a  motionless  condition  in  which  they 
resist  the  hot  and  dry  summer  winds.  Thus,  they  may  lie  for 
weeks,  and,  as  experimentation  has  shown,  they  may  be  dried 
for  several  years  (see  BUTSCHLI,  '89,  p.  1663,  for  references) 
without  loss  of  capacity  for  revivification.  The  same  device 

*  Thus  RAILLIET  ('02)  says  of  Strongylus  rufescens :  "I  have  seen  them 
regain  their  activity  after  42  and  even  68  days  of  desiccation.  However,  this 
activity  is  much  slower  in  manifesting  itself.  After  the  course  of  a  month  a 
contact  of  8  to  10  minutes  is  sufficient  to  bring  them  back  to  movement.  .  .  . 
After  68  days  at  least  50  minutes  are  required,  and  certain  individuals  have 
shown  activity  only  after  1  hour  and  20  minutes.  Moreover,  the  movements 
were  limited,  and  only  a  small  number  of  cases  contorted  themselves  like  ordi- 
nary Anguillulidse." 


J]  ACCLIMATIZATIOX   TO   DESICCATION  65 

>r  resisting  desiccation  is  seen  in  the  gemmules  of  sponges, 
id  Bryozoa,  the  eggs  of  many  animals,  and  the  spores  of  many 
mts.       Thus    some    protoplasm    normally   responds    to    the 
:imulus  of  drought  by  going  into  desiccation-rigor. 

While,  as  we  have  seen,  some  protoplasmic  bodies  may  be 
dried  as  far  as  possible  by  the  ordinary  methods  used  in  chem- 
istry without  death  ensuing,  other  bodies,  especially  the  adult 
forms  of  higher  organisms,  whose  cellular  respiration  is  de- 
pendent upon  a  circulating  fluid,  are  killed  by  desiccation. 
For  loss  of  this  fluid  or  desiccation-rigor  in  the  pumping 
muscles  will  produce  asphyxia.  But  these  conditions  do  not 
militate  against  the  belief  that  there  is  no  necessary  lower 
limit  to  the  amount  of  water  which  must  occur  in  quiescent 
protoplasm  in  order  that  it  may  retain  vitality  during  a  lim- 
ited period. 

§  3.    ON  THE  ACCLIMATIZATION  OF  ORGANISMS  TO 
DESICCATION 

We  have  seen  in  the  last  section  that  certain  organisms  are 
more  capable  of  resisting  desiccation  without  fatal  effect  than 
others;  e.g.  rotifers,  tardigrades,  and  Tylenchus.  Now  it  is 
clear  that  these  organisms  are  especially  apt  to  become  dried, 
so  that  it  is  possible  that  their  high  capacity  for  resistance  has 
been  produced  by  acclimatization  without  selection.  I  shall 
here  add  certain  other  cases  of  resistance  to  dryness  which  I 
believe,  but  cannot  prove,  to  have  been  thus  produced.  LANCE 
('94)  has  mentioned,  as  already  stated,  that  only  those  tardi- 
grades which  live  in  the  moss  of  gutters  (where  they  are 
alternately  wet  and  dried),  and  not  those  living  in  water,  show 
the  phenomenon  of  revivification.  CERTES  ('92)  has  found 
that,  although  marine  Ciliata  cannot,  in  general,  withstand 
desiccation,  those  from  the  chotts  and  saline  lakes  of  Algeria 
may  be  dried  like  those  from  fresh-water  ponds  and  swamps. 
The  difference  in  resistance  between  the  forms  dwelling  in 
the  sea  and  in  inland  salt-water  ponds  is  doubtless  due  to  the 
fact  that  the  former  are  not  regularly  desiccated,  while  the 
latter  are ;  consequently  the  latter  alone  have  had  a  chance  to 
become  acclimated  to  desiccation. 


66  MOISTURE  AND  PROTOPLASM  [Cn.  II 

§  4.    THE  DETERMINATION  OF  THE  DIRECTION  OF    MOVE- 
MENT BY  MOISTURE,  —  HYDROTAXIS 

This  phenomenon  has  been  described  by  STAHL  ('84)  in 
^Ethalium.  When  this  Myxomycete  is  placed  in  the  dark  upon 
a  glass  plate  covered  with  several  layers  of  moistened  filter 
paper,  it  expands  uniformly  over  the  homogeneously  moistened 
substratum.  If,  now,  the  plate  be  placed  in  a  drying  chamber, 
the  paper  dries  slowly,  and  one  can  see  that  the  mass  of  the 
plasmodium  draws  towards  those  places  which  remain  longest 
damp.  If  a  dilute  gelatine  jelly  is  smeared  upon  a  glass  slide 
supported  in  a  horizontal  position  about  2  mm.  above  the 
plasmodium,  still  in  the  dark  chamber,  the  plasmodium  sends 
up  branches,  some  of  which  may  touch  the  gelatine  and  spread 
out  over  it.  If  the  water  dries  still  further,  the  entire  Myxomy- 
cete may  become  transferred  to  the  slide  above.  If,  now,  the 
paper  be  moistened  again,  the  plasmodium  sends  branches  down 
to  it.  STAHL'S  explanation  is  that  of  the  old  mechanical 
school.  He  says,  the  peripheral  protoplasmic  layer  lying  next 
the  dryer  region  is  poorer  in  water;  while  that  next  the 
damper  part  of  the  substratum  contains  much  water.  If  it  be 
assumed  that  the  internal  streaming  tends  to  occur  uniformly 
towards  all  points  of  the  periphery,  it  is  clear  that  the  dryer, 
more  consistent  part  will  offer  greater  resistance  than  the  more 
fluid  part,  and  in  this  part,  therefore,  branches  will  tend  to 
arise.  In  correspondence  with  the  interpretations  which  we 
have  hitherto  placed  upon  similar  phenomena  I  prefer  to  call 
this  a  case  of  response  to  the  stimulus  of  excessive  moisture  — 
in  any  case  it  may  be  designated  positive  hydrotaxis. 

When,  however,  the  plasmodium  of  jEthalium  is  in  the  fruit- 
ing stage,  it  retreats  from  the  moister  part  of  the  substratum, 
and  other  Myxomycetes  in  the  fruiting  stage  show  the  same 
negatively  hydrotactic  tendency.  Thus  the  same  agent,  water, 
stimulates  the  same  organism,  at  different  stages,  to  reverse 
movements. 

I  will  now  summarize  the  conclusions  concerning  the  effect 
of  water  upon  protoplasm.  Water  constitutes  by  far  the  larger 
part  of  protoplasm  and  of  all  active  organisms.  Metabolism  is 


LITERATURE  67 

lireetly  dependent  upon  it,  and  certain  excretory  processes  are 
imulated  by  it.  The  motion  of  protoplasm  is  likewise  de- 
jndent  upon  water,  which  determines  the  unstable  condition 
that  substance.  Desiccation,  therefore,  produces  a  rigor, 
ind  this  may  continue,  in  the  absence  of  water,  for  months,  and 
even  years,  the  organism  being,  meanwhile,  ready  to  awake 
to  activity  upon  the  return  of  moisture.  The  degree  of  desic- 
cation which  organisms  can  resist  varies.  In  the  case  of  the 
higher  organisms,  it  is  slight ;  in  the  case  of  bodies  especially 
adapted  to  resist  dryness  (spores,  seeds,  statoblasts),  there  is, 
perhaps,  no  practicably  attainable  limit  to  the  dryness  which 
their  protoplasm  may  undergo  without  loss  of  power  of  revivifi- 
cation. The  condition  of  desiccation-rigor  is  not  known  to  be 
one  of  death  which  is  replaced  by  life  upon  return  of  moisture. 
It  is  probably  rather  a  condition  of  minimum  metabolism. 
The  great  resistance  capacity  exhibited  by  certain  organisms  is 
correlated  with  their  liability  to  desiccation  in  their  natural 
surroundings.  Finally,  Myxomycetes  (and  probably  other  or- 
ganisms) respond  to  inequalities  in  the  amount  of  moisture 
in  their  environment,  moving  either  towards  or  from  greater 
moisture.  We  recognize  thus  that  the  activities  of  protoplasm 
are  to  a  large  extent  dependent  upon  the  existence  of  water  in 
it ;  and  that  protoplasm  reveals  itself  as  sensitive  to  differences 
in  the  amount  of  moisture,  responding  by  secretions,  by  the 
assumption  of  a  quiescent  condition,  and  by  locomotion  with 
reference  to  water.  ' 


LITERATURE 

BLAINVILLE,  H.  DE  '26.  Sur  quelques  petits  Animaux  qui,  apres  avoir 
perdu  le  mouvement  par  la  dessication,  le  reprennent  comme  aupara- 
vant  quand  on  vient  a  les  mettre  dans  1'eau.  Ann.  des  Sci.  Nat.  IX, 
104-110. 

BEZOLD,  A.  VON  '57.  Untersuchungen  liber  die  Vertheilung  von  Wasser. 
organischer  Materie  und  anorganischen  Verbindungen  im  Thierreiche, 
Zeitsch.  f.  wiss.  Zool.  VIII,  487-524.  26  Feb.  1857. 

Bos,  R.  '88.  Untersuchung  iiber  Tylenchus  devastatrix,  KUHN.  Biol.  Cen- 
tralb.  VII,  646-659.  1  Jan.  1888. 

BROCA,  P.  '61.  Rapport  sur  la  question  soumise  a  la  Societe  de  Biologie 
par  MM.  POUCHET,  PENNETIER,  TIXEL  et  DOYERE  au  sujet  de  la  revi- 
viscence  des  animaux  desseches,  lu  par  M.  PAUL  BROCA  au  nom  d'une 


68  MOISTURE  AND  PROTOPLASM  [Cn.  II 

commission  comp.  de  MM.  BALBIANI,  BERTHELOT,  BROWN-SEQUARD, 

DARESTE,  GUILLEMIN,  CH.  ROBIN  et  BROCA.     Mem.  Soc.  de  Biol. 

(3),  1-139. 
BUTSCHLI,  O.  '89.    Protozoa  (part).    BRONN'S  Klass.  u.  Ord.  d.  Thier-reichs. 

I  Bd.  1585-2035.     1889. 
CERTES,  A.  '92.     Sur  la  vitalite  des  germes  des  organismes  microscopique 

des  eaux  douces  et  salees.     Bull.  Soc.  Zool.  France.     XVII,  59-62. 
DAVIS,  H.  '73.     A  New  Callidina :  with  the  Result  of  Experiments  on  the 

Desiccation  of  Rotifers.     Monthly  Micr.  Jour.     IX,  201-209.     1  May, 

1873. 
DEHNECKE,  C.  '81.     Einige  Beobachtungen  iiber  den  Einfluss  der  Prapa- 

rationsmethode  auf  die  Bewegungen  des  Protoplasma  der  Pflanzenellen. 

Flora.     LXIV,  8-14,  24-30.     1,  11  Jan.  1881. 
DOYERE,  M.  P.  L.  N.  '42.     Memoire  sur  les  Tardigrades.     Ann.  des.  Sci. 

Nat.     (2)  XVIII,  5-35. 
ENGELMANN,  T.  W.  '68.     Ueber  die  Flimmerbewegung.     Jena.  Zeitschr. 

IV,  321-479. 
FAGGIOLI,  F.  '92.     De  la  pretendu  reviviscence  des  Rotiferes.     Arch.  Ital. 

de  Biol.     XVI,  360-374.     31  Jan.  1892. 
FROMENTEL,  E.  DE  '77.     Recherches  sur  la  revivification  des  rotiferes,  des 

anguillules  et  des  tardigrades.      C.  R.  Assoc.  fran9-  1'avanc.  des  sci. 

VI  (Le  Havre),  641-657. 
GAVARRET,  J.  '59.     Quelques  experiences  sur  les  rotiferes,  les  tardigrades  et 

les  anguillules  des  mousses  des  toits.     Ann.  Sci.  Nat.  (Zool.).     (4),  XI, 

315-330. 

HUDSON,  C.  T.  '73.     Remarks  on  Mr.  Henry  DAVIS'  Paper  "On  the  Desic- 
cation of  Rotifers."     Monthly  Micr.  Jour.     IX,  274-276.      1  June, 

1873. 

'86.     [Desiccation  of  Rotifers.]     Jour.  Roy.  Micr.  Soc.     (2)  VI,  79. 
KOCHS,  W.  '90.     Kann  die  Kontinuitat  der  Lebensvorgange  zeitweilig  vol- 

lig  unterbrochen  werden?     Biol.  Centralbl.      X,  673-686.      15  Dec. 

1890. 
KRUKENBERG,  C.  F.  W.  '80.   Ueber  die  Vertheilung  des  Wassers,  der  organ- 

ischen  und  anorganischen  Verbindungen  im  Kb'rper  wirbelloser  Thiere. 

Vergl.-Physiol.  Stud.     I,  2  Abth.  78-106. 
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817,  818.     9  Apr.  1894. 
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Physiol.     XLIII,  71-157.     7  Apr.  1888. 
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1891. 
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LITERATURE  69 


RYWOSCH,  D.  '89.     Einige  Beobachtungen  an  Tardigraden.     Sb.  Naturf. 

Ges.  Dorpat.     IX,  89-92. 
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diger  Austrocknung  wieder  aufleben  oder  nicht?    Biol.  Centralb.     VI, 

230-235.     15  June,  1886. 


CHAPTER   III 

ACTION  OF  THE  DENSITY  OF   THE  MEDIUM  UPON 
PROTOPLASM 

IN  this  chapter  we  shall  consider  (I)  the  structure  of  proto- 
plasm and  the  physiological  action  of  solutions ;  (II)  the  effect 
of  density  upon  the  structure  and  general  functions  of  proto- 
plasm ;  (III)  acclimatization  to  solutions  of  greater  or  less 
density  than  the  normal ;  and  (IV)  control  of  the  direction  of 
locomotion  by  density  —  tonotaxis. 

§   1.    INTRODUCTORY   REMARKS  UPON  THE  STRUCTURE  OF 
PROTOPLASM  AND  THE  PHYSICAL  ACTION  OF  SOLUTIONS 

It  is  now  generally  recognized  that  protoplasm  consists  of 
two  substances  closely  interwoven  :  the  living  plasma  and  a 
watery  chylema.  The  relation  of  the  plasma  and  the  chylema 
is  still  a  debated  matter.  Since  the  only  theory  of  the  struct- 
ure of  protoplasm  which  has  been  experimentally  tested  is  that 
of  BUTSCHLI,  his  theory  is  especially  worthy  of  recognition. 
According  to  this  theory,  the  relation  of  plasma  and  chylema  is 
that  of  water  and  air  in  a  foam- work.  The  whole  protoplasmic 
mass  is  bounded  and  penetrated  through  and  through  by  plasma 
films  which  envelop  watery  globules.  It  is  with  membranes 
constructed  of  such  protoplasm  that  the  physical  phenomena 
of  osmosis  are  exhibited.* 

Osmosis  occurs  when  two  aqueous  solutions  of  different 
density  are  separated  by  an  animal  membrane,  f  Such  a  mem- 

*  Excellent  treatises  on  the  physical  and  chemical  nature  of  solutions,  in- 
cluding a  discussion  of  osmosis,  are  :  OSTWALD,  '91,  and  WHETHAM,  '95. 

t  Osmosis  occurs  likewise  when  such  solutions  are  separated  by  inorganic 
walls  containing  pores  of  extreme  fineness ;  e.g.  a  wall  of  porous  clay  in  which 
copper  ferrocyanide  has  been  precipitated. 

70 


1]  PHYSICAL  ACTION   OF   SOLUTIONS  71 

*ane  permits  the  free  passage  of  water,  but  not  of  the  dissolved 
ibstance,  or  rather,  of  the  dissolved  substance  but  slowly. 
rnder  these  conditions,  the  water  flows  more  rapidly  towards 
solution  containing  the  greater  number  of  molecules  (per  cc.). 
'he  theory  of  this  movement  is  that  upon  the  side  containing 
ie  greater  number  of  molecules  of  salt  fewer  water  molecules 
-ill  in  a  given  time  strike  the  membrane  than  upon  the  other 
side  ;    and  since  the  number  passing  through  is  proportional 
to  the  number  striking,  relatively  fewer  molecules  of  water 
will  consequently  pass  out,  and  so  there  will  be  a  resultant  flow 
of  water  to  that  side ;  and  if  the  mass  of  water  is  confined,  it 
will  exert  great  pressure. 

This  phenomenon  of  osmosis  plays  an  important  part  in 
organic  life.  Thus,  under  certain  conditions,  cells  take  in  the 
surrounding  water,  so  that  their  walls  are  put  under  tension 
(turgescence).  The  tension  thus  gained  may  be  considerable, 
amounting  to  6  or  7  atmospheres.  Under  other  conditions  the 
cells  give  up  their  water  to  the  surrounding  medium,  thus 
losing  their  turgescence.  This  occurs  when  they  are  put  into 
certain  solutions  of  KNO3  or  NaCl.  The  relation  between  the 
density  of  the  internal  and  external  fluids  thus  determines  the 
internal  pressure  experienced  by  the  cell. 

A  quantitative  method  of  determining  this  pressure  in  the 
presence  of  various  solutions  has  been  employed  by  PFEFFER 
('77).  Solutions  of  different  dry  salts  in  different  proportions, 
enveloped  by  a  semi-permeable  membrane,  were  placed  in  pure 
water,  and  the  pressure  upon  a  column  of  mercury  determined. 
It  was  found,  for  example,  that  with  a  1%  solution  of  cane 
sugar  a  pressure  of  47.1  cm.  of  mercury*  was  produced  ;  with 
a  1%  solution  of  K2SO4,  a  pressure  of  193  cm.  of  Hg.  He 
concluded,  as  a  result  of  his  various  experiments,  (1)  that  the 
pressure  is  proportional  to  the  concentration  of  the  solution, 
and  (2)  that  as  the  temperature  rises  the  pressure  increases. 

DE  VKIES  ('84)  made  a  noteworthy  advance,  using  plant 
cells  as  objects  of  experimentation  and  subjecting  them  to 
various  solutions  of  substances  freed  of  water.  He  determined 
the  degree  of  concentration  which  a  solution  of  KC1  must  have 

*  The  pressure  of  76  cm.  of  mercury  equals  that  of  1  atmosphere. 


72  SOLUTIONS  AND  PROTOPLASM  [Cn.  Ill 

in  order  that  no  endosmosis  or  exosmosis  should  occur  through 
the  cell  wall.*  He  next  determined  the  same  thing  for  some 
other  substances,  e.g.  KI,  and  found  that  the  degree  of  con- 
centration which  produces  no  osmosis  is,  for  two  different 
solutions,  proportional  to  the  molecular  weights  of  the  salts 
dissolved  in  them.  Solutions  which  produce  the  same  osmotic 
effect  DE  VRIES  called  isotonic.  A  solution  of  0.746%  KC1  is 
isotonic  with  a  solution  of  1.661%  of  KI,  for  the  molecular 
weight  of  KC1  is  74.6,  and  that  of  KI  is  166.1.  Thus  the  first 
result  which  DE  VRIES  gained  was  that  the  osmotic  effect  of 
solutions  of  salts  of  similar  structure  depends  upon  the  number 
of  their  molecules  in  the  solution. 

The  second  conclusion  of  DE  VRIES  was  that  salts  of  dis- 
similar structure  have  different  osmotic  properties,  even  when 
the  number  of  molecules  in  the  two  solutions  is  the  same. 
Thus,  he  found  that  with  an  equal  number  of  molecules  to  the 
solution  (molecular-weight  solutions  f  )  :  — 

(1)  All  salts  of  alkalis  with  one  atom  of  metal  to  the  molecule  are 

isotonic    (formula,    E'A9    [composed    of   a   monad   metallic 
radicle,  R,  and  a  monad  acidic  radicle,  A])  ; 

(2)  All  organic  compounds  with  no  metal  radicle,  have  two-thirds  the 

osmotic  action  of  the  first  group  ;  e.g.  cane  sugar,  C^H^Ou-  $ 


*  As  is  well  known,  when  a  fully  developed  plant  cell  is  put  into  a  strong 
saline  solution  the  living  plasma  sac  separates  from  the  cell  wall  and  contracts, 
eventually,  into  a  ball,  —  the  result  of  the  chylema  flowing  out  of  the  protoplasm 
(plasm  olysis)  .  The  weaker  the  concentration,  the  less  marked  the  plasmolytic 
phenomena.  Finally,  a  concentration  is  reached  so  weak  that  the  separation  of 
the  plasma  sac  hardly  occurs  or  is  limited  to  a  single  corner.  This  concentra- 
tion may  be  regarded  as  equal  to  that  of  the  cell-sap  —  as  that  at  which  no 
osmosis  occurs.  (See  Fig.  8.) 

t  I  shall  use  the  phrase  "  molecular-  weight  solution  "  to  indicate  solutions  in 
the  making  up  of  which  the  molecular  weight  of  the  substance  in  grammes,  dis- 
solved in  100  g.  of  water,  is  used  as  the  unit  of  concentration.  It  will  often  be 
convenient  to  abbreviate  it  as  MW%  sol.  Chemists  frequently  use  as  a  unit 
solution,  called  "normal"  solution,  the  molecular  weight  in  grammes  dissolved 
in  1000  g.  of  water.  Our  M  W  %  sol.  is  therefore  equal  to  one-tenth  of  a  "  normal  '  ' 
solution. 

J  The  fact  that  glycerine  can  be  absorbed  by  some  plants  has  introduced  a 
complexity  into  the  determination  of  its  isotonic  coefficient.  This  determina- 
tion has  been  made  the  subject  of  a  special  investigation  by  DE  VRIES  ('88),  who, 
by  the  use  of  slowly  absorbing  plants,  has  found  the  isotonic  coefficient  to  be  1.78, 
which  agrees  approximately  with  the  number  given  above  for  organic  compounds. 


§  1]  PHYSICAL   ACTION  OF  SOLUTIONS  73 

(3)  All  salts  of  alkalis  with  two  atoms  of  metal  to  the  molecule  have 

four-thirds  the  osmotic  action  of  (1)  (formula,  R2'A")',  e.g. 
K2S04. 

(4)  Salts  of  alkalis  with  three  atoms  of  the  metal  to  the  molecule 

have  five-thirds  the  osmotic  action  of  (1)  (formula,  RB'A'"); 
e.g.  K3(C6H507). 

In  other  words,  the  osmotic  action  of  groups  (2),  (1),  (3), 
and  (4)  are  in  the  proportions  of  2,  3,  4,  5.  These  last  num- 
bers are  the  Isotonic  Coefficients  of  DE  VRIES.  In  addition  to 
these  substances,  DE  VRIES  determined  that  the  isotonic  coeffi- 
cient is,  in  the  case  of  — 

salts  of  earthy  alkalis  with  1  acid  radicle ;  e.g.  MgS04     .     .     2 
salts  of  earthy  alkalis  with  2  acid  radicles ;  e.g.  CaCL, ...     4 

In  the  third  place  DE  VRIES  established  the  law  that  each 
acid  group  and  each  metal  has,  in  all  compounds,  the  same  par- 
tial isotonic  coefficients ;  the  coefficient  of  any  salt  is  the  sum 
of  these  partial  coefficients  of  the  constituent  components. 
These  partial  coefficients  are  :  — 

for  each  atom-group  of  an  acid 2 

for  each  atom  of  an  alkaline  metal  (Li,  Na,  K,  Kb,  Cs)      .     .     1 
for  each  atom  of  an  earthy  metal  (Ca,  Sr,  Ba,  Mg)  ....     0 

while  of  the  compounds  the  isotonic  coefficients  are  — 

KC1  =  1  +  2  =  3,  MgSO4  =0  +  2  =  2, 

K2S04  =  2x1  +  2  =  4,  MgCl2  =  0  +  2x2  =  4, 

K,(C6HA)  =  3x1+2  =  5,  etc. 

The  determination  of  isotonic  coefficients  has  subsequently 
been  extended  by  several  authors,  especially  by  HAMBURGER 
('86  and  '87)  and  by  MASSART  ('89). 

The  work  of  HAMBURGER  was  done  upon  blood  corpuscles. 
The  method  employed  by  him  was  as  follows  :  In  certain  weak 
solutions  the  haemoglobin  passes  out  of  the  red  blood  corpuscles 
of  ox  blood.  The  concentration  at  which  it  just  began  to  ex- 
trude was  determined  for  various  salts,  and  it  was  found  that 
these  concentrations  were  usually  proportional  to  the  molecular 
weights  of  the  substances  divided  by  certain  whole  numbers, 
which  are  the  same  as  the  isotonic  coefficients  of  DE  VRIES. 


74  SOLUTIONS   AND  PROTOPLASM  [Cn.  Ill 

The  work  of  MASSART  was  done  chiefly  upon  bacteria.  He 
made  use  of  the  fact  demonstrated  by  PFEFFER  (see  p.  41) 
that  substances,  which  at  a  low  concentration  attract  bacteria 
chemotactically,  at  a  higher  concentration  repel  them.  He 
found  that,  in  general,  the  repulsions  exercised  by  the  various 
dissolved  substances  are  proportional  to  their  isotonic  coef- 
ficients, when  the  solutions  are  made  up  as  MW  solutions. 
Thus,  when  a  10  MW  %  concentration  of  a  substance  with  iso- 
tonic coefficient  2  just  begins  to  repel  bacteria,  a  substance 
which  just  begins  to  repel  in  a  5  MW  %  concentration  has  an 
isotonic  coefficient  of  4.* 


§  2.   EFFECT  OF  VARYING  DENSITY  UPON  THE  STRUCTURE 
AND  GENERAL  FUNCTIONS  OF  PROTOPLASM 

Under  this  head  we  may  consider,  (a)  the  effect  upon  the 
general  structure  of  protoplasm ;  (5)  the  modification  of  gen- 
eral functions,  and  (<?)  the  production  of  death. 

*  Starting  from  the  observations  of  PFEFFER  and  DE  VRIES  the  modern  school 
of  physico-chemists  has  greatly  extended  our  knowledge  of  solutions.  As  a 
result  of  their  work  it  appears  that  the  validity  of  DE  VRIES'  law  will  not  hold 
strictly  for  all  solutions  at  all  concentrations.  For  the  number  of  effective 
particles  in  every  solution  of  electrolytes,  namely,  of  salts,  bases,  and  acids,  is 
greater  than  the  number  of  molecules  put  into  the  solution ;  because  a  certain 
proportion  of  the  dissolved  molecules  break  up  or  dissociate  into  their  constitu- 
ent tows,  and  the  osmotic  pressure  is  determined  by  the  number  of  both 
molecules  and  free  ions  in  the  solution.  In  the  case  of  sugar,  the  alcohols  and 
non-electrolytes  in  general,  no  dissociation  occurs.  In  a  normal  solution  of 
potassic  chloride,  on  the  other  hand,  75.5%  of  the  molecules  dissociate,  each 
forming  two  free  ions.  Since  24.5  %  of  the  molecules  are  intact  and  there  are 
151  free  ions  percent  of  the  molecules  introduced,  the  total  number  of  mole- 
cules and  free  ions  in  the  solution  is  175.5%  of  the  molecules  introduced  and 
the  osmotic  effect  of  a  normal  solution  of  KC1  is  1.755  times  that  of  a  normal 
solution  of  sugar.  The  percentage  of  molecules  of  any  electrolyte,  as  for 
instance  KC1,  which  dissociate  in  solution  increases  as  the  strength  of  the 
solution  diminishes,  eventually  becoming  100.  Thus,  in  one-half  the  normal 
solution,  78  %  of  the  molecules  of  KC1  dissociate  ;  at  0. 1  times  the  normal  solu- 
tion, 86%;  at  0.01,  94%;  at  0.001,  98%.  Also,  the  percentage  of  molecules 
dissociated  in  normal  solutions  of  different  electrolytes  varies.  Thus,  in  such  a 
solution  of  NaCl,  67.5%  of  the  molecules  are  dissociated;  of  LiCl,  61%;  of 
CaCl2,  53%  (each  into  3  ions)  ;  of  MgCl2,  40%;  of  KI,  79%;  of  MgSO4,  19%; 
of  Na2SO4,  35.6  %  (each  into  3  ions) ;  and  so  on.  Valuable  and  extensive  tables 
for  the  determination  of  the  percentage  of  dissociation  at  different  concentrations 
will  be  found  in  WHETHAM,  '95. 


2] 


EFFECT  OX  STRUCTURE  AND  FUNCTIONS 


75 


a.  Since  a  protoplasmic  mass  is  bounded  by  a  Him,  permit- 
ling  osmosis,  it  is  clear  that  its  characters  may  be   greatly 
Ltered  by  varying  the  degree  of  concentration  of  the  solution 
which  it  lives ;  and  we  have  already  seen  that  they  are  so 
llerecl. 

When  plant  cells,  with  a  rigid  cell-wall,  are  put  into  dense 
xLutions,  the  water  is  drawn  from  the  protoplasmic  sac  which, 
mtracting,  is  torn  from  the  cell- wall.  The  salt  solution  pene- 
trates through  the  latter,  but  cannot  enter  the  bounding  plasma- 
film,  which  continues  to  contract  around  the  diminishing  glob- 
le  of  water  until  only  a  small  ball  remains. 


FIG.  8.  —  1.  Young,  not  more  than  half-grown,  cells  from  the  cortical  parenchyma 
of  Cephalaria  lencantha.  2.  The  same  cell  in  a  4%  solution  of  potassium  nitrate. 
3.  The  same  cell  in  a  6%  solution.  4.  The  same  cell  in  a  10%  solution.  1  and  4 
from  nature,  2  and  3  diagrammatic,  all  in  optical  longitudinal  section,  h,  cell 
membrane ;  p,  lining  layer  of  protoplasm ;  k,  cell  nucleus ;  c,  chlorophyll  bodies : 
s,  cell-sap ;  e,  salt  solution  which  has  penetrated  within  the  cell-membrane.  (From 
SACHS  :  Pflanzenphysiologie,  after  DE  VBIES.) 

Put  into  pure  water,  on  the  contrary,  the  protoplasmic  sac 
becomes  distended,  provided  the  cell  sap  contains  an  appro- 
priate solution,  generally  a  plant-acid.  Thus  turgescence  is 
brought  about. 

The  same  effect  of  varied  density  upon  the  structure  of  pro- 
toplasm is  observable  among  animals  also.  Thus,  KUHKE 
('64,  p.  48)  and  CZERXY  ('69,  pp.  158, 161)  found  that  Amoeba 
shrinks  into  a  spherical  mass  when  put  into  a  \%  to  2%  NaCl 
solution,  and,  when  returned  to  fresh  water,  swells.  Also,  the 
character  of  the  pseudopodia  of  Amoeba  and  Myxomycetes 
changes.  They  become  more  numerous  and  attenuated,  so  that 


76  SOLUTIONS   AND   PROTOPLASM  [Cn.  Ill 

the  whole  form  of  the  organism  has  been  likened  to  a  horse- 
chestnut  with  its  shell  on.  (KUHNE,  '64,  pp.  48,  83 ;  CZERNY, 
'69,  p.  159.)  ZACHARIAS  ('84,  p.  254,  and  '88)  has  described  a 
similar  phenomenon  in  the  spermatozoon  of  Polyphemus  pedicu- 
lus.  When  put  into  a  3%  NaCl  solution  the  spermatozoa  lost 
their  cylindrical  form  and  protruded  long  pseudopodia.  A 
remarkable  fact  about  the  pseudopodia,  moreover,  was  that  in 
locomotion  they  were  used  like  flagella.  Likewise,  FABRE- 
DOMERGUE  ('88,  p.  102)  and  MASSART  ('89)  have  observed 
that  the  protoplasm  of  encysted  Ciliata  swells  or  contracts 
according  as  it  is  placed  in  a  less  or  more  dense  medium  ;  the 
cyst  thus  being  perfectly  permeable  by  water.  MASSART  has, 
indeed,  obtained  a  rough  quantitative  expression  of  this  state- 
ment, which  is  given  in  Tables  X  and  XI,  p.  87.  HAMBUR- 


FIG.  9.  —  Blood  corpuscles  of  the  frog.  1,  2,  normal;  3,  4,  5,  various  degrees  of 
plasmolysis  by  solutions,  a,  nucleus  and  shrunken  plasma;  b,  water-filled 
spaces.  (From  HAMBURGER,  '87.) 

GER  ('87)  has  found  that  dense  solutions  produce  the  same 
modifications  upon  blood-corpuscles  (see  Fig.  9). 

Again,  GRUBER  ('89)  has  found  those  individuals  of  the 
heliozoon  Actinophrys  sol  which  live  in  fresh  water  different 
from  those  which  live  in  the  sea,  and  he  has  produced  that  dif- 
ference artificially.  In  the  marine  variety  the  plasm  is  dense, 
granular,  free  from  vacuoles ;  while  that  of  the  fresh-water 
kind  is  extraordinarily  rich  in  vacuoles,  and  has  even  a  foamy 
appearance.  If  a  marine  form  is  gradually  accustomed  to  fresh 
water  its  protoplasm  soon  acquires  a  vacuolated  structure  which 
renders  it  indistinguishable  from  the  fresh- water  one.  GRUBER 
also  accustomed  fresh-water  Actinophrys  to  sea  water,  when  it 
acquired  the  structure  of  the  normal  marine  form.  Likewise 
the  marine  Amoeba  crystalligera,  which  has  a  dense  protoplasm, 
becomes  vacuolated  after  being  accustomed  to  fresh  water. 
Also,  SCHMANKEWITSCH  ('79)  has  found  that  when  the  fresh- 


§2]  EFFECT  ON  .STRUCTURE   AXD   FUNCTIONS  77 

water  flagellate  Anisonema  acinus,  BUTSCHLI,  is  cultivated  for 
many  generations  in  water  to  which  sea  salt  is  gradually  added, 
its  structure  is  modified  with  the  increasing  density. .  The  in- 
dividuals become  smaller  and  their  feeding  canal  is  not  well- 
formed.  Another  change,  which  has  been  studied  only  in 
Vertebrates,  is  loss  of  weight.  BERT  ('71)  found  that  a  gold- 
fish plunged  into  sea  water  loses  67%  of  its  weight,  and  that 
young  eels  lose  10%  to  17%.  This  fact  also  is  clearly  what 
we  should  expect  from  the  theory  of  action  of  solutions,  accord- 
ing to  which  the  weak  solutions  of  the  body  cavity  should  lose 
water.  Thus,  the  changes  produced  in  the  structure  of  proto- 
plasm by  more  or  less  dense  solutions  are  chiefly  the  results  of 
osmosis. 

b.  Among  the  functions  of  protoplasm,  general  movements 
(with  locomotion)  and  excretion  seem  to  be  most  markedly 
affected  by  density.  Thus,  KUHXE  ('64,  p.  48)  found  that,  when 
first  subjected  to  a  1%  NaCl  solution,  the  movements  of  Amoeba 
became  more  lively  for  a  moment.  ENGELMANX  ('68,  p.  343) 
noticed  the  same  acceleration  in  movement  in  the  cilia  of  the 
epithelium  lining  the  frog's  oesophagus  when  subjected  to  pure 
water  —  hence,  to  a  weaker  solution  than  the  normal  cell  fluid. 
Even  after  death,  fresh  water  causes  a  transitory  activity  in 
the  cilia.  In  all  cases,  after  a  minute  or  two  (1%  solution)  the 
movements  begin  to  diminish,  until  at  last  they  cease.  This 
cessation  of  movement,  whether  due  to  loss  or  imbibition  of 
water,  is  not  necessarily  death.  For,  if  the  abnormal  con- 
centration has  not  acted  for  too  long  a  time,  the  movements 
return  when  the  protoplasm  is  placed  again  in  its  normal  fluid. 
(KUHXE,  '64,  p.  48;  EXGELMAXN,  '68,  p.  343.)*  At  a  certain 

*  A  similar  cessation  of  movement  occurs  when  the  lower  organisms  are  sub- 
jected in  water  to  very  great  pressures.  Experiments  upon  this  phenomenon 
have  been  made  chiefly  by  REGNAKD  ('84,  '84a-'84d,  and  '86),  CERTES  ('84, 
'84a),  and  ROGER  ('95).  REGNARD  was  able,  by  the  use  of  a  special  apparatus, 
to  subject  beer  yeast,  in  water,  during  1  hour,  to  a  pressure  of  1000  atmospheres 
(about  1000  kilograms  per  sq.  cm.).  When  yeast  so  subjected  was  then  placed  in 
sugared  water,  it  showed  at  first  no  activity.  It  was  not  dead,  however,  but  had 
fallen  into  a  latent  life  ;  for  1  hour  after  it  had  been  relieved  from  pressure  it 
revived  and  fermentation  set  in.  Some  algge,  Infusoria,  and  actinians,  subjected 
to  600  atmospheres  during  10  to  60  minutes,  or  to  300  atmospheres  for  24  hours 
(CERTES,  '84),  exhibited  a  similar  temporary  rigor.  Likewise  muscle  at  200  to 


78  SOLUTIONS  AND  PROTOPLASM  [Cn.  Ill 

strength,  however,  varying  for  different  individuals  (ENGEL- 
MANN,  CZERNY),  death  rapidly  ensues.  Thus  Amoeba  quickly 
breaks  up  in  a  10%  solution,  and  the  ciliated  epithelium  of  a 
frog's  throat  in  a  2.5%  solution.  Four  phases  in  the  action  of 
concentrations  may  thus  be  observed  :  stimulation,  retardation, 
density-rigor,  and  death.  Even  in  concentrations  at*  which 
motion  is  not  entirely  inhibited,  locomotion  may  be  interfered 
with.  Thus,  RICHTER  ('92,  pp.  37-40)  found  that  while  normal 
Tetraspora  swarm-spores  move  at  the  rate  of  about  60//,  per 
second,  or  else  rotate  about  100  times  per  minute,  those  in  an 
11%  solution  hardly  move  from  their  place,  or  sometimes 
move  one-eleventh  as  fast  as  the  normal  swarm-spores.  While 
it  is  possible  that  the  dense  water  affords  a  mechanical  obstacle 
to  locomotion,  it  seems  more  probable  that  it  is  the  general 
diminution  of  activities  which  causes  the  slow  migration. 

The  modification  of  excretion  by  abnormal  concentrations 
has  been  studied  especially  by  ROSSBACH  ('72).  This  experi- 
menter worked  upon  fresh- water  Ciliata  (which  alone  possess  a 
contractile  vacuole)  by  subjecting  them  to  a  0.5%  solution  oft 
NaCl.  The  contractile  vacuole  became  diminished  almost  to 
invisibility,  and  the  interval  between  contractions  was  in- 
creased. In  a  1%  solution  of  sugar  a  reduction  in  size  of  the 
contractile  vacuole  occurred,  but  this  was  not  so  marked  as  in 
the  case  of  the  1%  NaCl  solution.  This  is  what  we  should 
expect  according  to  theory,  for  the  number  of  molecules  in  a 
1%  solution  of  sugar  (mol.  wt.,  342)  is  much  less  than  in  a  1% 
solution  of  NaCl  (mol.  wt.,  58.5),  and  their  relative  osmotic 

action  is  as        2        :  - — |— -,  or  as  0.002  :  0.017,  or  as  2  :  17. 
o  X  o4^      o  X  Oo.o 

The  phenomenon  of  contracting  vacuoles  seems  not  to  be 
confined  to  Protozoa.  It  occurs  in  the  embryos  of  some  Mol- 
lusca,  especially  the  stages  of  fresh-water  Pulmonates,  upon 
which  my  friend,  Dr.  KOFOID,  performed  some  density  experi- 
ments. The  early  cleavage  and  blastula  stages  of  many  fresh- 
water Pulmonates  contain  a  central  fluid-filled  vacuole,  which 

300  atmospheres  loses  its  contractility,  and  at  400  atmospheres  becomes  rigid 
and  hard.  It  also  increases  immensely  in  weight  by  the  addition  of  water. 
ROGER  pointed  out  that,  subjected  for  2  minutes  to  a  pressure  of  3000  kilograms 
per  sq.  cm. ,  certain  bacteria  (Streptococcus)  are  even  killed. 


-2]  EFFECT  ON  STRUCTURE  AND  FUNCTIONS  79 

undergoes  periodic  enlargement  and  discharge  as  in  the  case  of 
the  contractile  vacuole.  KOFOID  ('95,  p.  104)  found  that 
when  eggs  of  Physa  and  Amnicola  were  placed  in  a  0.19%  or 
0.10%  XaCl  solution,  the  contents  of  the  central  cavity,  once 
extruded,  were  not  so  quickly  restored  as  in  the  control  eggs, 
and  that  the  maximum  volume  attained  by  the  vacuole  in  the 
salt  solution  was  less  than  that  attained  in  fresh  water.  For 
example,  "  the  cavity  of  the  control  eggs  attained  a  diameter  of 
5  to  7  units,  while  that  of  the  eggs  in  the  salt  solution  was 
only  3  to  4  at  the  time  of  elimination.  There  were,  however, 
a  very  few  cases  in  which  the  cavity  reached  a  diameter  of  5 
units."  Of  interest  is  the  additional  fact  that  marine  Gastro- 
poda do  not  seem  to  have  a  "  cleavage  "  cavity,  but  that  this  is 
confined  to  eggs  developing  in  fresh  water  or  moist  situations. 

The  effect  of  density  upon  the  higher  animals  is  very  com- 
plex, according  to  the  observations  of  BERT  ('71)  upon  the 
gold-fish.  Plunged  into  sea  water  it  shows  violent,  unco- 
ordinated movements ;  then  it  becomes  immobile,  and  rises  to 
the  surface  by  virtue  of  its  relatively  lower  specific  gravity. 

The  effect  of  fresh  water  upon  marine  organisms  is  equally 
striking,  as  GOGORZA*  ('91)  has  shown.  They  go  immediately 
to  the  bottom  and  move  with  difficulty.  Swimming  animals 
swim  badly  if  at  all,  and  small  fishes  have  to  make  much  exer- 
tion to  rise  to  the  surface.  The  sensibility  also  undergoes 
great  changes.  Many  animals  soon  become  lethargic.  Echino- 
derms  and  molluscs  act  as  if  anaesthetized,  since  they  do  not 
respond  as  quickly  as  usual  to  external  stimuli,  and,  finally, 
pass  into  complete  paralysis.  The  action  is  slower  upon 
Crustacea  and  fish;  but  here,  too,  fresh  water  acts  as  an  an- 
aesthetic. The  respiratory  movements  become  deep  and  rapid, 
bivalves  extend  their  branchiae,  and  Crustacea  beat  the  water 
rapidly  with  their  appendages  in  order  to  renew  the  supply. 
Animals  ordinarily  transparent,  like  medusse,  become  opaque ; 
first  externally,  then  internally.  The  cornea  of  fish  becomes 
opaque  and  the  external  slime  coagulates.  The  tissues  become 
swollen,  so  that  soft-bodied  animals  are  visibly  deformed  —  in 


*  For  an  abstract  of  the  work  of  GOGORZA,  I  am  indebted  to  the  kindness  of 
Mr.  F.  C. 


80 


SOLUTIONS  AND  PROTOPLASM 


[Cn.  Ill 


fishes  the  eyes  are  forced  out,  the  foot  of  gastropods  swells,  the 
blood  corpuscles  swell  up  and  burst,  and  muscular  tissue  may 
increase  as  much  as  6  times  in  volume.  The  enlargement  of 
the  different  tissues  is  exhibited  in  the  following  table,  which 
shows  the  percentage  increase  in  weight  and  volume  of  organs 
of  Scyllium  canicula,  placed  in  fresh  water. 


AFTER  2  HOURS. 

AFTER  94  HOURS. 

%  Increase  in 
Weight. 

%  Increase  in 
Volume. 

%  Increase  in 
Weight. 

%  Increase  in 
Volume. 

Muscular  tissue  .... 

15 

50 

20 

200 

Glandular  tissue  .  .  . 

12 

0 

19 

100 

Nervous  tissue  .... 

20 

50 

60 

250 

All  of  these  phenomena  are  clearly  explicable  upon  the  assump- 
tion of  their  production  by  endosmosis. 

c.  The  pressure  due  to  dense  solutions  may  become  very 
great,  amounting,  as  I  have  said,  to  many  atmospheres.  So  it 
is  not  surprising  that  a  change  of  medium  may  rend  cells  or 
at  any  rate  kill  organisms.  This  result  may  be  brought  about 
either  when  the  denser  solution  is  inside  of  the  body  or  outside  ; 
the  former  case  is  realized  when  marine  animals  are  plunged 
into  fresh  water,  the  latter  when  fresh-water  animals  are 
plunged  into  solutions  of  salts.  Studies  upon  the  fatal  effects 
of  varying  the  concentration  of  solutions  have  been  made  by 
BERT  ('66),  PLATEAU  ('71),  COUTANCE  ('83),  RINGER  and 
BUXTON  ('85),  DE  VARIGNY  ('88),  MASSART  ('89),  GOGORZA 
('91),  and  RICHTER  ('92). 

BERT'S  ('66)  studies  were  made  upon  marine  fish  which  he 
plunged  into  fresh  water.  In  a  vessel  holding  4.8  litres  of 
fresh  water,  a  mullet  died  in  44  minutes,  and  a  Sparus  in  86 
minutes.  Since  the  fishes  lived  longer  in  a  sugar  solution, 
BERT  concluded  that  death  was  due  to  diminished  density  of 
the  medium.  In  this  conclusion  he  was  nearer  the  truth  than 
his  immediate  followers  in  this  work. 

PLATEAU'S  ('71)  observations  were  made  upon  all  classes  of 
Invertebrates,  but  especially  upon  Arthropods.  He  subjected 


2] 


EFFECT   ON   STRUCTURE   AND  FUNCTIONS 


81 


them  to  solutions  both  more  and  less  dense  than  the  normal, 
and  determined  their  resistance  periods.  As  a  result  of  sub- 
jecting fresh- water  animals  to  salt  solutions,  he  found  that 
their  resistance  period  diminished  approximately  as  the  thick- 
ness of  the  skin  {and  cuticula)  diminished.  Thus,  when  plunged 
into  sea  water  (3.046%  salts)  adult  water  insects  resisted  in- 
definitely ;  insect.  larv«e  6  to  4  hours ;  Entomostraca  less  than 
an  hour  ;  Nephelis,  5  to  7  minutes  ;  Planaria,  4  minutes ;  and 
Hydra  only  1  minute.  GOGORZA  ('91)  got  similar  results,  find- 
ing the  resistance  capacity  of  the  different  groups  to  diminish  in 
this  order  :  molluscs,  crustaceans,  fish,  worms,  tunicates,  echino- 
derms,  coelenterates.  So  we  may  consider  this  relation  between 
resistance  period  and  thickness  of  covering  a  general  law  of 
resistance  ;  and  it  is  what  we  should  expect  upon  the  theory 
that  the  solutions  act  osmotically. 

By  subjecting  organisms  to  separate  solutions,  each  contain- 
ing 3%  of  the  various  salts  found  in  sea  water,  PLATEAU  was 
able  to  show  that  NaCl  produced  the  most  important  effect, 
MgCl2  the  next  most  important  effect,  and  MgSO4  still  less. 
This  is  shown  by  the  following  — 

TABLE  IX 

RESISTANCE  PERIODS  OF  FRESH-WATER  CRUSTACEA  TO  VARIOUS  CONSTITUENTS 
OF  SEA  SALT.     TEMPERATURE  NOT  GIVEN 

(Numbers  indicate  minutes  elapsing  before  death  occurred) 


3%NaCl. 

3%MgCl2. 

3%MgS04. 

MOL.  WT.,  58.5; 

MOL.     WT.,    95; 

MOL.    WT.,    120; 

SEA 

SPECIES. 

I.C.,  3;  OSMOTIC 

I.C.,  4  ;  OSMOTIC 

I.C.,  2;  OSMOTIC 

WATER. 

IXDEX,  —  . 

INDEX,  -1. 

INDEX,  -?-. 

58.5 

95 

120 

Gammarus  roeselii.  . 

105 

131 

520 

230 

Asellus  aquaticus    .  . 

155 

1162 

2000 

160 

Daphnia  sima    .... 

7.8 

19.5 

87 

22 

Cyclops  quadricornis 

12.1 

37 

690 

257 

Cypris  fusca 

267 

223 

460 

36 

Although  from  this  table  it  seems  clear  that  there  is  an 
inverse  relation  between  resistance  period  and  osmotic  index, 
PLATEAU  did  not  believe  that  the  death  of  the  animals  experi- 


82  SOLUTIONS  AND  PROTOPLASM  [Cn.  Ill 

men  ted  upon  was  due  alone  to  the  osmotic  action  of  the  salts. 
To  this  conclusion  he  was  led  by  an  unfortunately  devised 
experiment.  He  compared  the  action  of  several  pairs  of  solu- 
tions, one  of  the  members  of  the  pair  being  a  salt,  and  the 
other  member  sugar,  the  dissolved  substance  of  each  having 
the  same  gross  weight.  In  all  cases  the  action  of  the  salt 
was  the  more  powerful.  But  this  is  what  we  should  expect 
upon  the  theory  that  death  is  caused  by  osmosis,  since  the 
osmotic  index  of  sugar  is  far  lower  than  that  of  any  of  the  salts 
with  which  comparison  was  made. 

Let  us  now  ascertain  the  relation  between  the  resistance 
period  and  the  "osmotic  index."  To  determine  the  relative 
resistance  periods  for  any  species  in  the  different  salts,  we  may 
take  as  our  unit  the  average  resistance  period  to  all  the  salts, 
and  express  the  separate  resistance  periods  in  terms  of  that 
unit.  To  determine  the  osmotic  index,  we  divide  the  isotonic 
coefficient  by  the  molecular  weight.  The  resistance  periods 
will  vary  inversely  as  the  osmotic  indices.  For  the  salts,  NaCl, 
MgCl2,  MgSO4,  the  reciprocals  of  the  osmotic  indices  are  :  19.6, 
23.8,  58.8  ;  and  the  mean  relative  resistances  are  :  19,  63,  217. 
From  this  comparison  it  is  seen  that  while  the  reciprocals  of 
the  osmotic  indices  increase  roughly  from  1  to  3,  the  relative 
resistance  period  increases  from  1  to  11 ;  or  the  resistance 
period  increases  more  rapidly  than  the  reciprocals  of  the  osmotic 
indices,  and  roughly  as  the  squares  of  those  reciprocals. 

At  about  the  same  time  with  PLATEAU'S  work  was  published 
that  of  BERT  ('71).  The  work  of  the  latter  was  done  chiefly 
upon  fresh- water  fishes ;  incidentally,  upon  frogs  and  some 
fresh-water  Arthropoda.  These  were  plunged  directly  into 
sea  water,  and  their  resistance  periods  determined.  Some 
species  showed  an  extraordinary  variability  in  their  resistance 
period ;  sticklebacks  (Gasterosteus  leiurus)  from  the  same 
locality  (about  Paris)  resisting  for  from  2  hours  to  1  month 
or  more. 

A  decided  advance  was  made  by  BERT  in  observing  that  the 
resistance  period  varies  with  the  temperature ;  thus,  the 
European  minnow  (Phoxinus  Isevis)  died  in  sea  water  — 

at    9°  C.  in  30  minutes,  at  22°  C.  in  14  minutes,' 

at  14°  C.  in  25  minutes,  at  28°  C.  in    9  minutes. 


§2] 


EFFECT   OX  STRUCTURE   AND  FUNCTIONS 


83 


Thus,  in  this  case  there  is  a  diminution  in  the  resistance  period 
of  approximately  1  minute  for  every  degree  of  increase  in  the 
temperature. 

Similar  observations  have  been  made  by  others.  GOGORZA 
('91,  p.  242)  finds  that  in  all  animals,  at  a  low  temperature,  the 
resistance  period  is  2  to  3  times  as  long  as  at  a  high  temperature. 

In  connection  with  these  facts,  it  is  to  be  noted  that  osmotic 
pressure  increases  with  temperature,  indeed,  is  proportional  to 
the  absolute  temperature.  (OsxwALD,  '91,  p.  114.)  But  as 
we  are  not  able  to  say  what  relation  exists  between  osmotic 
pressure  and  resistance  period,  we  cannot  say  whether  the  above 
table  agrees  with  the  physical  law. 

Finally,  we  may  discuss  the  question  of  the  relation  between 
the  strength  of  the  solution  and  the  length  of  the  resistance 
period.  Data  for  this  discussion  are  afforded  by  the  extensive 
observations  of  GOGORZA.  This  author  disclaims  having  found 
any  mathematical  relation,  but  his  tables,  properly  treated,  do 
show  such  a  relation.  The  resistance  periods  depend  upon  so 
many  factors  that  the  times  obtained  by  subjecting  one  animal 
to  different  concentrations  of  a  salt  cannot  be  directly  compared 
with  those  obtained  from  another  animal.  It  is  the  relative 
resistance  periods  only  that  can  be  thus  compared.*  GOGORZA'S 
concentrations  were  obtained  by  subjecting  marine  animals  to 
mixtures  of  marine  and  fresh  water.  No.  1  contained  100% 
sea  water;  No.  2,  75%;  No.  3,  66%;  No.  4,  50%;  No.  5,  33%; 
No.  6,  25%;  No.  7,  0%.  Averaging  the  relative  lengths  of 
life  of  22  species  which  died  in  75%,  or  weaker  percents  of 
sea  water,  and  comparing  with  the  percentage  of  salts  in  various 
concentrations  (the  density  of  Mediterranean  sea  water  being 
taken  as  1.037),  we  get  — 


Xo.  OF  SOLUTION  : 

! 

2 

3 

4 

5 

6 

7 

%  of  salt  in  solution  .... 

3.7 

2.8 

2.5 

1.9 

1.2 

0.9 

0.00 

Rel.  resist,  per.  .  . 

Indef 

500 

283 

10.83 

5.44 

3.46 

1.84 

Log.  of  rel.  res.  per  

1.7 

1.45 

1.04 

0.73 

0.54 

Log.  rel.  res.  per.  x  1.7   .  . 

2.9 

2.5 

1.7 

1.2 

0.9 

*  The  relative  resistance  periods  are  calculated  by  the  method  described 
>n  p.  82. 


84 


SOLUTIONS  AND  PROTOPLASM 


[Cn.  Ill 


The  curve  shown  in  Fig.  10  is  constructed  from  the  second 
and  third  lines  of  this  table.  The  table  shows  that,  within  the 
limits  of  2.8%  and  0.9%  concentration,  the  curve  is  a  logarith- 
mic one,  i.e.  as  the  ordinates  increase  the  abscissae  increase 
as  the  logarithms  of  the  ordinates.  In  line  4  are  given 

the  (BRIGGS')  loga- 
rithms of  the  num- 
bers in  line  3,  and 
in  line  5  these  loga- 
rithms are  each  mul- 
tiplied by  a  constant, 
1.7,  which  gives  a 
series  of  numbers 
closely  similar  to 
that  of  line  2.  The 
relation  between 
density  and  resist- 
ance period  can  thus 
be  expressed  by  the 
equation 

D  =  k.  log.  R, 

in  which  D  stands  for 
density ;  R,  for  re- 
sistance period;  and 
k  is  a  constant  whose 
value  depends  upon 
the  system  of  loga- 
rithms employed. 

This  formula  may  be 
2 
",  in  which   e  is  the 

Since   the 


40 
30 
20 
10 

0 
< 

FK 

| 

/ 

/ 

/ 

\f\ 

i 

/ 

i 

/ 

/ 

OA 

/ 

7 

1 

I 

1 

on 

/ 

/ 

/ 

1 

J 

/ 

/ 

/ 

r 

/ 

—  —  • 

.  — 

jn 

" 

J                   .9      1.2             1.9           2.5    2.8                  3.7 
}.  10.  —  Curve  showing  relation  between  the  per- 

centage  of  salt  in  mixtures  of  fresh  and  salt  water 
(abscissae)  and  the  mean  resistance  periods  in  hours 
of  various  organisms  plunged  therein  (ordinates). 
Constructed  from  the  table.  (After  data  of  Go- 
GORZA,  '91.) 


transformed  into  the   equivalent:    R  = 

base    of    the    NAPERIAN    system    of    logarithms. 

osmotic  pressure  is  proportional  to  the  concentration  (p.  71), 

Q 

it  follows  also  that  R  =  ek>  where  0  stands  for  the  osmotic 
pressure  and  k'  for  a  new  constant.  The  same  relation  holds 
when  we  compare  the  reciprocals  of  the  relative  resistance 
periods  —  or  the  relative  rapidity  of  killing  —  and  the  abso- 
lute diminution  of  concentration. 


ACCLIMATIZATION 


85 


3.  ACCLIMATIZATION  TO  SOLUTIONS  OF  GREATER  OR  LESS 
DENSITY  THAN  THE  NORMAL 

In  the  preceding  section  we  saw  that  different  organisms  had 
diverse  resistance  period  to  the  same  density  of  solution.  In 

rt,  this  may  be  accounted  for,  as  we  have  seen,  on  the  ground 

a  difference  in  the  rapidity  of  osmotic  action  —  thick-skinned 
inimals  resisting  longer  than  thin-skinned  ones.  All  diversity 

the  effect  of  solutions,  cannot,  however,  be  accounted  for  on 
is  ground.  Thus,  the  molluscs  of  the  sea  and  those  of  fresh 
ater  appear  to  have  an  equally  pervious  epidermis,  yet  the 
rruer  will,  of  course,  withstand  a  much  stronger  solution  of 
lt  than  the  latter.  This  difference  in  resistance  capacity 
ems  closely  correlated  with  the  conditions  of  the  medium  in 
hich  the  organism  has  been  reared.  Thus,  BEUDANT  ('16) 
und  that  littoral  species  (living,  therefore,  in  a  part  of  the  sea 
here  the  water  is  much  diluted  by  rivers),  e.g.  Ostrea,  Mytilus, 
atella  vulgata,  resist  fresh  water  better  than  deep-sea  species; 

d   this   discovery   has    been    abundantly   confirmed    by   DE 

AKIGNY  ('88).* 

That  the  conditions  of  density  of  the  culture  medium  deter- 
ine  the  resistance  capacity  is  proven  by  experiment,  for,  by 
rying  the  density  of  the  culture  solution,  we  may  vary  the 

istance  period  of  the  individuals  experimented  on.  BEUDANT 
16)  was  the  first  to  show  this.  He  used  Lymnea,  Physa, 
lanorbis,  Ancylus,  Paludina,  and  some  other  fresh-water  Mol- 
sca.  He  began  in  April  by  putting  these  organisms  into  a 
XaCl  solution,  and,  continuing  to  add  salt  slowly,  by  Sep- 
mber  many  of  these  withstood  a  4%  solution  —  a  solution 
kills  animals  suddenly  subjected  to  it.  He  performed 

ewise  the  reverse  experiment  upon  marine  Mollusca  (Patella, 


extremes  of  density  in  which  organisms  are  capable  of  living  are  often 
nsiderable.     On  the  one  hand,  the  individuals  of  some  species,  especially  fish, 
able  to  migrate  from  fresh  to  salt  water  and  back,  with  impunity.     On  the 
er  hand,  many  species  of  a  family,  the  other  members  of  which  are  marine, 
ve  become  accustomed  to  fresh  water.     Examples  of  this  last  case  are  the 
droid  Cordylophora  lacustris,  the  mollusc  Dreissena,  and  the  endoproctan 
ozoan  Urnatella.     Likewise,  some  marine  species  have  come  to  live  in  exces- 
ively  salt  water.     Such,  for  example,  is  the  case  with  Artemia  salina  which 
ives  in  Salt  Lake,  Utah,  containing  over  22%  of  salts.     (LEIDY,  '72,  p.  165.) 


86  SOLUTIONS  AND  PROTOPLASM  [Cn.  Ill 

Turbo,  Area,  Cardium  edule,  Mytilus  edulus,  etc.)  bringing 
them  to  live  in  fresh  water  by  gradually  diluting  the  medium. 

PLATEAU  ('71)  gradually  accustomed  the  fresh-water  Asel- 
lus  aquaticus  to  pure  sea  water,  so  that  even  in  mixtures  con- 
taining between  20%  and  80%  of  sea  water  they  laid  eggs  and 
produced  a  second  generation.  The  second  generation  lived 
108  hours  in  pure  sea  water,  while  Asellus  freshly  taken  and 
plunged  into  sea  water  live  only  about  5  hours. 

Not  only  the  larger  organisms,  but  also  tissues  and  Protozoa 
may  become  acclimated.  ROTH  observed  in  '66  (p.  190)  that 
cilia  become  "accommodated"  to  gradually  increasing  densi- 
ties ;  ENGELMANN  ('68,  p.  343),  however,  denied,  though  with- 
out critical  experiments,  the  validity  of  this  conclusion  for  the 
case  of  the  ciliated  epithelium  of  the  frog's  throat.  Later, 
CZERNY  ('69,  p.  161)  succeeded  in  acclimating  Amoeba  to  a  4% 
solution  of  NaCl,  although  Amoeba  rarely  resists  1  %  when  sud- 
denly subjected  to  it. 

These  early  experiments  have  since  been  greatly  extended, 
observations  having  been  made  upon  nearly  all  groups  of  organ- 
isms —  upon  algae,  by  RICHTER  ('92)  ;  upon  Myxomycetes,  by 
STAHL  ('84) ;  upon  Actinospherium,  by  VERWORN  ('89,  p.  10) ; 
upon  bacteria,  Flagellata,  Ciliata,  and  Hydra,  by  MASSART 
('89);  upon  Ciliata,  by  FABRE-DOMERGUE  ('88);  upon  Crus- 
tacea, by  PLATEAU  ('71),  SCHMANKEWITSCH  ('75  and  '77), 
and  BERT  ('83);  upon  the  tadpoles  of  frogs,  by  YUNG  ('85, 
p.  520) ;  and  upon  representatives  of  almost  all  of  the  principal 
groups,  by  BE  VARIGNY  ('88)  and  GOGORZA  ('91). 

The  aims  and  methods  of  these  experimenters  have  been 
very  diverse.  Some  have  sought  merely  to  illustrate  how 
marine  organisms  may  have  come  to  live  in  fresh  water,  or  the 
reverse.  Such  have  usually  made  mixtures  of  fresh  and  salt 
water,  the  proportions  of  the  one  gradually  increasing  (DE 
VARIGNY,  SCHMANKEWITSCH,  GOGORZA),  or  they  have  added 
sea  salt,  dry  or  in  solution,  to  the  normal  fresh-water  medium 
of  the  organism  (YUNG).  MASSART,  on  the  other  hand,  having 
in  mind  the  more  fundamental  problem  of  the  action  of  density 
upon  protoplasm,  has  employed  solutions  of  a  single  salt  at  a 
time  —  solutions,  moreover,  based  usually  upon  the  osmotic 
index  of  the  salt  as  a  unit  of  concentration. 


§3] 


ACCLIMATIZATION 


87 


Athough  there  has  been  a  gradual  improvement  in  methods, 
the  conditions  other  than  that  of  concentration  have  too  often 
been  omitted  from  consideration.  The  omission  of  the  tempera- 
ture of  the  experiment  solutions  is  especially  unfortunate,  for 
according  to  GoGORZA  ('91,  p.  270),  acclimatization  is  more 
easily  effected  at  a  low  temperature  than  at  a  high  one. 

Of  the  papers  mentioned  above,  that  of  MASS  ART  is  especially 
worthy  of  extended  notice  from  its  quantitative  nature.  He 
subjected  cysts  of  Ciliata  to  various  concentrations  of  KNO3 
and  noted  the  effect  upon  the  protoplasm.  In  the  following 
tables,  the  first  line  of  numbers  names  the  solution  in  parts  of 
the  molecular  weight  expressed  in  grammes.  The  symbols  in 
the  columns  headed  by  these  numbers  have  the  following  signifi- 
cations: 0,  no  effect;  v,  the  cysts  possess  a  large  vacuole  whose 
pulsations  are  infrequent;  v p,  the  vacuole  is  still  prominent 
but  plasmolysis  is  occurring ;  p,  the  plasmolysis  is  more  marked 
and  the  vacuole  is  gone;  P,  the  plasmolysis  is  so  marked  that 
the  form  of  the  infusorian  is  lost.  The  results  given  in  the 
third  and  fourth  lines  were  obtained  from  individuals  acclimated 
for  22  hours  to  a  1.8  MW  %  and  to  a  3  MW  %  solution  of 
KXO3  respectively.  The  observations  were  made  immediately 
after  immersion  of  the  cysts.  No  mention  is  made  of  the 
temperature. 

TABLE   X  —  VORTICELLA 


HUXDREDTHS   OF   MOLECULAR   WEIGHT. 

O.5 

1.0 

1.5 

2.0 

2.5 

3.O 

3.5 

4.O 

5.O 

Unacclimated 

y 

V 

V  D 

V  V 

<n 

P 

P 

Acclimated  to  1.8  %  

v  Jr 

V  JJ 

V 

r 

v  p 

V  V 

P 

P 

P 

Acclimated  to  3.0  %  

v  p 

P 

P 

P 

TABLE   XI  — COLPODA 


HUXDREDTHS   OF  MOLECULAR   "WEIGHT. 

0.5 

l.O 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

5.0 

Unacclimated  

o 

V 

y 

V 

y 

V 

V 

Acclimated  to  1.8  MW%.  .  .  . 

0 

V 

V 

vp 

P 

P 

Acclimated  to  3.0  MW%.  .  .  . 

V 

P 

P 

P 

88  SOLUTIONS  AND   PROTOPLASM  [Cn.  Ill 

If  we  take  as  our  unit  in  Table  X  the  concentration  repre- 
sented by  v  p,  and  in  Table  XI  the  concentration  represented 
by  v,  we  may  conclude  that  the  subjection  for  22  hours  to  a 
1.8  MW  %  or  to  a  3  MW  %  solution  of  the  salt  has  given  a 
resistance  capacity  of  between  2  and  3  times  the  normal.* 

The  question  now  arises,  what  is  the  cause  of  this  increased 
resistance  capacity  ?  It  is  not  merely  apparent,  resulting  from 
the  selection  of  the  more  resistant  individuals,  thus  elevating 
the  mean.  It  is  clearly  due  to  a  diminution  in  the  intensity  of 
osmosis;  and  this  must  be  due  to  the  establishment  of  an  equi- 
librium between  internal  and  external  osmotic  pressures. 

Now,  this  equilibrium  can  only  be  brought  about  by  the 
density  of  the  internal  fluids  becoming  equal  to  that  of  the 
external  medium;  and  this  requires  that  the  salt  held  in  solu- 
tion shall  traverse  the  bounding  protoplasmic  films,  gaining 
the  interior.  That  such  a  traversing  occurs  has  been  argued 
by  MASSART  ('89),  who  has  himself  produced  new  evidence  for 
this  conclusion.  As  is  well  known  numerous  pigments  in 
solution  penetrate  to  the  nucleus  of  the  living  protist.  Potassic 
nitrate  (JANSE,  '87,  p.  22),  glycerine,  and  urea  (DE  VRIES, 
'88  and  '89)  have  been  observed  to  penetrate  protoplasm. f 
That  NaCl  does  the  same  thing  has  been  shown  by  many 
observers.  Thus,  EMERY  ('69)  found  that  when  a  frog  is 
placed  in  a  salt  solution  and  is  left  there  for  some  time,  then 
rinsed  in  water  until  no  salt  appears  in  the  washings,  and, 
finally,  put  into  pure  water,  salt  is  given  forth  from  the  epider- 
mis (precipitation  on  adding  silver  nitrate).  Likewise  PLATEAU 
('71,  p.  20)  found  that  various  fresh- water  Arthropods  reared 
in  a  salt  solution  excreted  an  unusual  amount  of  salt ;  and 
FREDERIC  ('85)  has  determined  that  the  quantity  of  salt  in  the 
blood  of  Carcinus  varies  from  3.1%  to  1.5%,  according  to  the 

*  A  few  data  concerning  proper  acclimatization  cultures  to  NaCl  may  be 
found  useful.  To  acclimate  bacteria  0.003  to  0.009  MW  %  may  be  added  daily  ; 
Oscillaria,  0.01  MW  %,  added  monthly  ;  Anabaena  and  Tetraspora,  0.018  M W  %, 
added  monthly  ;  Ciliata,  0.003  MW  %,  daily  ;  Hydra  viridis,  0.001  MW  %,  daily 
for  6  days  ;  Tubifex,  0.02  MW  %,  daily ;  tadpoles,  0.004  to  0.014  MW  %,  daily. 

t  A  fact  observed  by  BERT  ('71)  suggests  that  some  solids  are  taken  into  the 
body  in  acclimatization  ;  for,  he  says,  fresh-water  fishes  acclimatized  to  sea 
water  gain  in  weight,  and  when  placed  in  fresh  water  fall  to  the  bottom.  The 
fact  that  they  fall  to  the  bottom  indicates  that  their  specific  gravity  is  increased. 


§  4]  TOXQTAXIS  89 

density  of  the  salt  solution  in  which  it  has  been  reared.  Finally, 
MASS  ART  has  shown,  by  a  new  method,  that  several  soluble 
organic  compounds  can  permeate  the  bounding  cell-film  of 
Flagellata.  Thus,  if  after  permanently  plasmolyzing  Polytoma 
uvella  by  a  0.02  MW  %  solution  of  KNO3,  a  0.01  MW  %  solu- 
tion of  saccharose  be  added  to  the  solution,  the  protoplasm  soon 
regains  its  normal  form,  apparently  by  absorption  of  saccharose, 
since  the  cell- wall  is  impermeable  to  KXO3.  By  the  same 
method,  potassium  acetate,  calcium  butyrate,  calcium  phosphate, 
glycerine,  ammonium  tartrate,  asparagine,  glycose,  sodium 
benzoate,  salicin,  and  phloridzin  can  be  shown  to  permeate  the 
protoplasm  of  this  flagellate.  All  these  facts  point  to  the  con- 
clusion to  which  physicists  had  arrived  concerning  dead  animal 
membranes,  that  protoplasm  admits  the  slow  penetration  of  the 
dissolved  salts,  and  thus  effects  the  eventual  equilibration  of 
internal  and  external  densities. 

In  conclusion,  a  word  may  be  said  concerning  variability  in 
capacity  of  acclimatization.  The  data  afforded  upon  this  sub- 
ject by  RICHTER  ('92)  are  the  most  valuable.  He  was  able  to 
acclimatize  Tetraspora  to  16%  (0.27  MW  %)  NaCl,  while 
Spirogyra  would  not  withstand,  under  like  treatment,  0.5% 
(0.0085  MW  %).  It  is  clear  then  that,  just  as  the  resistance 
capacity  varies,  so  also  does  the  acclimatization  capacity. 


§  4.    CONTROL  OF  THE  DIRECTION  OF  LOCOMOTION  BY 
DENSITY  :  TONOTAXIS 

Three  authors  only,  so  far  as  I  know,  have  concerned  them- 
selves with  this  phenomenon, — STAHL  ('84),  PFEFFER  ('84,  '88), 
and  MASS  ART  ('89,  '91).  STAHL  ('84)  observed  that  plasniodia 
of  Myxomycetes  withdrew  from  solutions  either  denser  or  less 
dense  than  the  normal,  and  concludes  that  the  action  is  not  a 
simple,  directly  explicable  one,  but  is  rather  a  highly  compli- 
cated irritability  phenomenon.  The  observations  of  PFEFFER 
were  incidental  to  his  study  of  chemotaxis.  He  found  that 
high  concentrations  of  many  substances  acted  repulsiv.ely,  and 
he  was  at  first  ('84,  p.  455)  inclined  to  attribute  this  repulsion 
to  osmotic  action,  but  later  ('88,  p.  624)  he  believed  this  view 
disproved.  The  disproof  he  considered  to  lie  in  this,  that 


90  SOLUTIONS  AND  PROTOPLASM  [On.  Ill 

the  repulsive  quality  varies  with  the  quality  of  the  substance 
—  may  occur  even  in  substances  which  are  not  attractive  at 
any  concentration.  PFEFFER  is,  therefore,  inclined  to  regard 
strong,  repelling  solutions  as  acting  in  a  different  fashion  from 
attractive  ones.  Just  as  strong  sunlight  may  repel  organisms 
attracted  by  weak  light,  —  both  phenomena  being  light  phe- 
nomena, —  so  the  repulsion  and  attraction  of  solutions  may 
both  be  regarded  as  chemical  phenomena. 

The  work  of  MASSART  brought  evidence  against  PFEFFER'S 
conclusions,  and  added  many  important  data.  His  studies 
were  made  chiefly  upon  bacteria,  to  a  less  degree  upon  Flagel- 
lata,  Hydra,  the  frog,  and  the  human  conjunctiva.  The  results 
of  the  studies  showed  that  neutral  solutions  of  a  certain  con- 
centration repel,  and  that  the  repulsion  is  proportional  to  their 
isotonic  coefficients  and  inversely  proportional  to  their  molecu- 
lar weights,  and,  therefore,  that  the  repulsions  are  purely 
osmotic  phenomena. 

The  conclusions  of  MASSART  thus  summarized  were  obtained 
by  the  use  of  special  methods,  which  gave  quantitative  results. 
So  they  are  worth  detailed  consideration.  A.  drop  of  liquid 
containing  bacteria  is  suspended  from  the  under  side  of  a 
cover-glass  in  a  moist  chamber  whose  side  walls  are  formed  of 
cardboard,  and  whose  top  is  the  cover-glass.  Into  the  drop, 
glass  capillary  tubes  similar  to  those  used  by  PFEFFER  are  in- 
troduced, filled  with  the  solution  whose  action  is  to  be  studied. 
In  addition  to  this  solution  all  the  tubes  should  contain  T00500-Q 
MW  %  (0.00691  gr.  %)  K2CO3  for  the  purpose  of  attracting 
the  bacteria.  When  a  tube  containing  only  this  dilute  solution 
of  K2CO3  is  put  into  the  drop,  bacteria  crowd  into  it  and  liter- 
ally fill  it  in  from  20  to  30  minutes.  But  when  a  series  of 
increasing  solutions  of  a  neutral  salt  like  NaCl  is  added  to  the 
K2CO3,  the  organisms  at  first  do  not  crowd  in  so  rapidly,  then 
remain  at  the  mouth,  and,  finally,  are  repelled  from  the  tube 
opening.  MASSART  has  tabulated  the  results  obtained  with 
Spirillum  upon  using  tubes  containing  different  chemical  sub- 
stances in  different  degrees  of  concentration.  One  of  these 
tables,  in  slightly  modified  form,  is  reproduced  here.  In  this 
table,  A  indicates  that  the  bacteria  entered  the  tube  readily ; 
a,  that  they  merely  gathered  about  its  mouth  ;  0,  that  they 


TONOTAXIS 


91 


were  repelled.     The  numbers  at  the  heads  of  the  columns  are 


the  different  values  of  n  in  the  formula, 


n 


1000 


Since 


the  different  solutions  were  made  up  on  the  basis  of  molecular 
weights,  all  solutions  of  a  given  concentration  contained  the 
same  number  of  molecules. 

TABLE  XII 


ISMTUN.    COEF.    3. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

XH4C1   .... 

A 

A 

A 

a 

a 

0 

0 

0 

0 

o 

XaCl  

A 

A 

A 

A 

a 

a, 

o 

o 

o 

o 

KCX  

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

KC1           .  .  . 

A 

A 

A 

A 

a. 

a 

o 

o 

o 

o 

XH4X03  .  .  . 

A 

A 

A 

A 

a 

a 

0 

0 

o 

0 

XaX03  .... 

A 

A 

A 

A 

a 

d 

a 

0 

0 

0 

KXOo 

A 

A 

A 

A 

d 

d 

Q 

Q 

Q 

o 

KBr    

A 

A 

A 

A 

a. 

o 

o 

o 

o 

0 

KClOo    .... 

A 

A 

A 

A 

a 

o 

0 

0 

o 

o 

KI    

A 

A 

A 

A 

ci 

a 

o 

o 

o 

0 

From  this  table  it  appears  that,  as  a  rule,  solutions  of 
MW  %  and  over  are  repelled,  while  those  of  10400  or  under, 
except  in  the  case  of  KCN,  permit  the  free  migration  of  the 
bacteria  into  the  tube. 

In  the  case  of  those  substances  whose  isotonic  coefficient  is 
4,  solutions  of  yoVo  ^W  %  and  over  always  repel,  and  those  of 
10300  in  the  majority  of  cases  permit  free  migration.  In  the 
case  of  those  substances  whose  isotonic  coefficient  is  2,  solutions 
of  over  y^j-Q  MW  %  repel,  and  those  of  under  y^o"  usually 
permit  free  migration.  The  solutions  at  which  repulsion  just 
occurs  in  the  three  cases  are  in  the  ratio  10  :  7  :  6 ;  which  is 
nearly  the  same  ratio  as  the  reciprocals  of  the  isotonic  coef- 
ficients, which,  multiplied  by  2  run,  10:6.6:5.  Thus  the 
conclusion  seems  justified  that  the  repelling  action  of  these 
substances  is  proportional  to  their  isotonic  coefficients,  and  is, 
therefore,  probably  osmotic  in  its  nature. 

In  a  second  work,  MASSAKT  ('91)  has  studied  this  matter 
with  the  aid  of  new  methods.  A  drop  of  sea  water  containing 
bacteria  is  prepared  as  before,  on  a  cardboard  ring,  but,  in  place 


92 


SOLUTIONS  AND  PROTOPLASM 


[Cn.  Ill 


of  a  capillary  tube  containing  a  dense  solution,  grains  of  NaCl 
are  placed  at  one  point  of  the  margin  of  the  drop.  These 
grains  gradually  dissolve,  their  molecules  gradually  diffuse 
through  the  drop,  and  as  they  do  so  the  bacteria  retreat  before 
them,  remaining  in  the  zone  of  least  concentration.  Again,  a 
drop  of  distilled  water  was  placed  alongside  of  the  drop  of  sea 
water  containing  Spirillum,  and  the  two  drops  were  connected 
by  a  communicating  canal  of  water  (Fig.  11).  As  the  dis- 


Distilled  water.  Distilled  vcater.  Distilled  water. 

FIG.  11.  —  A  drop  of  sea  water  connected  with  a  drop  of  distilled  water  (in  lower  part 
of  diagrams) .  The  marine  bacteria  of  the  former  retreat  before  the  encroachment 
of  the  latter.  (From  MASSART,  '91.) 

tilled  water  mingles  with  the  sea  water  at  one  mouth  of 
the  communicating  canal,  the  bacteria  retreat  further  and  fur- 
ther from  that  mouth,  keeping  in  the  most  concentrated  part 
of  the  drop.  Finally,  when  a  drop  of  sea  water  is  connected 
with  one  of  distilled  water,  and  granules  of  NaCl  are  placed 
in  the  drop  of  sea  water,  the  bacteria,  retreating  from  the  zone 
of  too  great  concentration  penetrate  into  the  drop  of  distilled 
water  (Fig.  12),  where  they  now  find  the  proper  concentration. 
Thus,  Spirillum  is  sensitive  both  to  solutions  denser  and  to 
those  weaker  than  the  normal  (hyperisotonic  solutions  and 
hypisotonic  solutions,  MASSART). 

In  summing  up  the  observations  of  this  section,  we  notice 
that  some  organisms  (for  MASSART  found  some  non-sensitive 
bacteria)  are  sensitive  to  concentration.  This  sensitiveness  is 


LITERATURE 

CINa  ClNa  ClXa 


93 


CINa 


IG.  12. —  A  drop  of  sea  water  joined  by  a  canal  with  a  drop  of  distilled  water.  The 
density  of  the  sea  water  is  being  gradually  increased  in  the  successive  figures  by 
the  dissolution  of  grains  of  salt  placed  at  one  edge.  As  the  solution  thickens,  the 
organisms  (marine  Anophrys,  represented  by  dots)  retreat  towards  the  distilled 
water.  (From  MASSART,  '91.) 

ich  that  they  are  repelled  by  either  hyperisotonic  or  hypiso- 
)iiic  solutions ;   only  in  a  certain  concentration  do  they  come 
rest.      We  may  speak  of   these    organisms   as   attuned   to 
s  concentration.      Different  organisms  are  attuned  to  dif- 
ferent concentrations,  and  there  can   be   no   doubt   that   the 
legree  of  concentration  to  which  they  are  attuned  is  deter- 
lined  by  the  past  experience  of  the  organisms,  as  the  facts 
)f  acclimatization  indicate. 


LITERATURE 

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'71.     Sur  les  phenomenes  et  les  causes  de  la  mort  des  animaux  d'eau 

douce  que  Ton  plonge  dans  1'eau  de  mer.     Comp.  Rend.     LXXIII, 

382-385 ;  464-467.     Aug.  1871. 
'73.     La  mort  des  animaux  d'eau  douce  que  1'on  immerge  dans  1'eau  de 

mer.     C.  R.  Soc.  de  Biol.,  Paris.     XXIII,  59-61. 
'83.     Sur  la  cause  de  la  mort  des  animaux  d'eau  douce  qu'on  plonge  dans 

1'eau  de   mer  et  reciproquement.     Comp.   Rend.     XCYII,   133-136. 

16  July,  1883. 
JEUDANT,  F.  S.  '16.     Memoire  sur  la  possibilite  de  faire  vivre  des  Mol- 

lusques  fluviatiles  dans  les  eaux  salines,  etc.    Jour,  de  Phys.    LXXXIII, 

268-284.     1816. 
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Protoplasma.     Leipzig.     232  pp.     1892. 


94  SOLUTIONS  AND  PROTOPLASM  [On.  Ill 

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XXXVI,  220-222. 
'84a.     De  1'action  des  hautes  pressions  sur  les  phenomenes  de  la  putri- 

faction  et  sur  la  vitalite  des  micro-organismes  d'eau  douce  et  d'eau  de 

mer.     Comp.  Rend.     XCIX,  385-388.     25  Aug.  1884. 
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de  vue  de  1'entretien  des  animaux  marins.     Bull,  de  la  Soc.  d'Acclimat. 

(3)  X,  98-106.     Feb.  1883. 
CZERNY,  V.  '69.     Einige  Beobachtungen  iiber  Ambben.     Arch,  f .  mik.  Anat. 

V,  158-163. 
EMERY,  H.  '69.     Notes  physiologiques.     Ann.  des  Sci.  Nat.  (Zool.).     (5) 

XII,  305-325. 

ENGELMANN,  T.  W.  '68.     (See  Chapter  II,  Literature.) 
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infusoires  cilies.     Ann.  des  Sci.  Nat.     (7)  V,  1-140. 
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HAMBURGER,  -H.  J.  '86.     Ueber  den  Einfluss  chemischer  Yerbindungen  auf 

Blutkbrperchen  im   Zusammenhang  mit  ihren  Molecular-Gewichten. 

Arch.  f.  Anat.  u.  Physiol.,  Physiol.  Abth.  Jahrg.  1886.     476-487. 
'87.     Ueber  die  durch  Salz-  und  Rohrzucker-Lb'sungen  bewirkten  Ver- 

anderungen  der  Blutkorperchen.     Arch.  f.  Anat.  u.  Physiol.,  Physiol. 

Abth.  Jahrg.  1887.     31-50. 
JANSE,  J.  M.  '87.     Plasmolytische  Versuche  an  Algen.     Bot.  Centralbl. 

XXXII,  21-26. 
KOFOID,  C.  A.  '95.     On  the   Early  Development  of  Limax.     Bull.  Mus. 

Comp.  Zool.     XXVII,  35-118. 
KUHNE,  W.  '64.     (See  Chapter  I,  Literature.) 
LEIDY,  J.  '72.     On  Artemia  from  Salt  Lake,  Utah.     Proc.  Acad.  Nat.  Sci. 

Philad.  1872.     164-166. 

MASSART,  J.  '89.     Sensibilite  et  adaption  des  organismes  a  la  concentra- 
tion des  solutions  salines.     Arch,  de  Biol.     IX,  515-570. 
'91.     (See  Chapter  I,  Literature.) 
OSTWALD,  W.  '91.     Solutions.     Translated  by  MUIR.     316  pp.     London  i 

Macmillan.     1891. 
PLATEAU,  F.  '71.    Recherches  physico-chlmiques  sur  les  articules  aquatiques. 

Mem.  cour.  1'Acad.  Roy.  Belgique.     XXXVI,  68  pp. 
PFEFFER,  W.  '77.     Osmotische  Untersuchungen.     Leipzig.     1877. 
'84.     (See  Chapter  I,  Literature.) 
'88.     (See  Chapter  I,  Literature.) 


LITERATURE  95 

REGXARD,  P.  '84.     Recherches  expefimentales  sur  1'influence  des  tres  hautes 

pressions  sur  les  organismes  vivants.     Comp.  Rend.     XCVIII,  745- 

7-47.     21  March,  1884. 
'84a.     Note  sur  les  conditions  de  la  vie  dans  les  profondeurs  de  la  mer. 

C.  R.  Soc.  de  Biol.     XXXVI,  164-168. 
'84b.     Note  relative  a  Faction  des  hautes  pressions  sur  quelques  pheno- 

menes  vitaux  (mouvement  des  cils  vibratiles,  fermentation).    C.  R.  Soc. 

de  Biol.     XXXVI,  187-188. 
'84C.     Sur  la  cause  de  la  rigidite  des  muscles  soumis  aux  tres  hautes 

pressions.     C.  R.  Soc.  de  Biol.     XXXVI,  310-311. 
'84d.     Effe\t  des  hautes  pressions  sur  les  auimaux  marins.     C.  R.  Soc.  de 

Biol.    XXXVI,  394-395. 
'86.     Action  des  hautes  pressions  sur  les  tissues  animaux.     Comp.  Rend. 

CII,  173-176. 
RICHTER,  A.  '92.     Ueber  die  Anpassung  der  Siisswasseralgen  an  Kochsalz- 

losungen.     Flora.     L,  4-56. 
RIXGER,  S.   and  BUXTOX,  D.  W.  '85.     Concerning  the  Action  of  Small 

Quantities  of  Calcium,  Sodium,  and  Potassium  Salts  upon  the  Vitality 

and  Function  of  Contractile  Tissue  and  the  Cuticular  Cells  of  Fishes. 

Jour,  of  Physiol.     VI,  154-161.     July,  1885. 
ROGER,  H.  '95.     Action  des  hautes  pressions  sur  quelques  bacteries.     Arch. 

de  Physiol.     (5)  VII,  12-17.     Jan.  1895. 
ROSSBACH,  M.  J.  '72.     (See  Chapter  I,  Literature.) 
ROTH,  M.  '66.     Ueber  einige  Beziehungeii  des  Flimmerepithels  zum  con- 

tractilen  Protoplasma.     Arch.  f.  path.  Anat.  u.  Physiol.     XXXVII, 

184-194.     Oct.  1866. 
SCIIMANKEWITSCH,  V.  '75.     Ueber  des  Verhaltniss  der  Artemia  salina  Miln. 

Edw.  zur  Artemia  Miihlhausenii  Miln.  Edw.  und  dem  Genus  Bran- 

chipus  Schaeff.     Zeitschr.  f.  wiss.  Zool.     XXV,  Suppl.,  103-116. 
'77.     Zur  Kenntniss  des  Einflusses  der  ausseren  Lebensbedingungen  auf 

die  Organisation  der  Thiere.     Zeitsch.  f.  wiss.  Zool.     XXIX,  429-494. 

6  Sept.  1877. 

'79.     [Abstr.  in  Nature.     XXIX,  274.     1884.] 
STAHL,  E.  '84.     (See  Chapter  I,  Literature.) 
VARIGXY,  H.  DE  '88.     Beitrag   zum    Studium  des   Einflusses   des  siissen 

Wassers  auf  die  Seethiere.      Centralbl.  f.  Physiol.     I,  566-568.     21 

Jan.  1888. 

VERWORX,  M.  '89.     (See  Chapter  I,  Literature.) 
VRIES,  H.  DE  '84.     Eine  Methode  zur  Analyse  der  Turgorkraft.     Jahrb.  f . 

wiss.  Bot.     XIV,  427-601. 
'88.     Le  Coefficient  Isotonique  de  la  Glycerine.    Arch.  Neerland.     XXII, 

384-391. 
'89.     Ueber  die  Permeabilitat  der  Protoplaste  fur  Harnstoff.  Bot.  Ztg. 

XL VII,  309. 
WHETHAM,  "W.  C.  D.  '95.     Solutions  and  Electrolysis. .  Cambridge  Nat.  Sci. 

Man.     Cambridge,  Eng.     296  pp.     1895. 


96  SOLUTIONS  AND  PROTOPLASM  [Cn.  Ill 

YUXG,  E.  '85.     De  1'influence  des  variations  du  milieu  physico-chemique  sur 

le  developpement  des  animaux.     Arch.  Sci.  phys.  et  nat.     (3)  XIV, 

502-522.     15  Dec.  1885. 
ZACHARIAS,  O.  '84.     Ueber  die  amoeboiden  Bewegungen  der  Spermatozoen 

von   Polyphemus  pediculus  de   Geer.     Zeitschr.   f.   wiss.   Zool.     XLI, 

252-258. 
'88.     Ueber  Pseudopodien  und  Geisseln.     Biol.  Centralbl.     VIII,  548, 

549.     15  Nov.  1888. 


CHAPTER  IV 

ACTION  OF  MOLAR  AGENTS   UPON  PROTOPLASM 

THIS  subject  is  so  ill-defined  that  it  is  impossible  to  draw 
any  line  of  distinction  between  contact  on  the  one  hand  and 
a  crushing  pressure,  or  wounding,  on  the  other.  The  molar 
agents  may  be  solid  or  fluid.  The  methods  of  application  may 
vary  from  a  blunt  contact  or  a  sharp  cut  or  puncture  to  the 
impact  of  flowing  liquid.  All  these  agents  have  this  in  common, 
however,  that  they  act  in  a  gross,  mechanical  way.  The  sub- 
ject will  be  discussed  under  the  following  heads :  (I)  The 
effect  of  molar  agents  upon  lifeless  matter;  (II)  effect  upon 
the  metabolism  and  movement  of  protoplasm ;  and  (III)  effect 
in  determining  the  direction  of  locomotion,  —  thigmotaxis 
(stereotaxis)  and  rheotaxis. 

§  1.    EFFECT  OF  MOLAR  AGENTS  UPON  LIFELESS  MATTER 

Mechanical  disturbance  can  induce  in  certain  lifeless  com- 
pounds violent  chemical  changes.  Compounds  which  are  so 
affected  are  preeminently  unstable.  This  instability,  however, 
varies  greatly  in  degree.  In  some  cases,  the  blow  of  a  hammer 
is  required  to  upset  the  molecules  ;  the  result  being  often  a 
violent  explosion.  In  other  cases  (#•#•  chloride  or  iodide  of 
nitrogen),  the  slightest  touch  of  a  feather  suffices  to  produce 
an  explosion.  Now,  most  of  the  substances  which  explode 
upon  impact,  and  which  are  used  in  the  arts,  are  organic  com- 
pounds, —  fulminate,  nitro-glycerine,  gun-cotton,  and  picric- 
acid  derivatives,  —  and  therefore  it  is  not  surprising  that  we 
find  the  notoriously  unstable  protoplasm  violently  affected  by 
contact. 

Especially  important  for  biology  is  the  fact  that  undulatory 
motions  and  other  periodic  disturbances  produce  very  important 
H  97 


98         MOLAR  AGENTS  AND  PROTOPLASM      [Cn.  IV 

molecular  changes  in  chemical  compounds.  Certain  substances 
have  a  specific  rate  of  vibration,  so  that  when  this  is  reproduced 
by  a  vibrating  cord  or  plate,  explosion  of  the  substance  may 
occur.  Iodide  of  nitrogen  is  one  of  these  substances  which  is 
exploded  by  a  high  note.  (CHAMPION  and  PELLET,  72,  p.  212.) 
Upon  this  property  of  explosive  compounds  depends,  apparently, 
the  efficacy  of  "detonators,"  the  explosion  of  a  small  quantity 
of  which  is  capable  of  producing  the  explosion  of  -a  great  mass 
of  a  second  compound.  Living  protoplasm  is,  likewise,  espe- 
cially affected  by  periodic  disturbances,  and  it  is  doubtless  due 
to  the  peculiarities  of  its  chemical  structure  that  the  auditory 
epithelium  is  so  affected  by  sound  waves  in  all  their  modifica- 
tions of  pitch,  volume,  and  timbre. 

§  2.    EFFECT  OF   MOLAR  AGENTS   UPON  THE  METABOLISM 
AND  MOVEMENT  OF  PROTOPLASM 

We  shall  first  consider  the  effect  on  metabolism,  and  then  on 
movement.  The  principal  metabolic  effects  that  will  be  con- 
sidered are  phosphorescence  and  secretion. 

The  phosphorescence  of  organisms  is  usually  regarded  as  a  slow 
combustion  (oxidation)  of  organic  substances.  This  chemical 
process  is  apparently  accelerated  by  mechanical  irritation,  as 
every  one  must  have  noticed  who  has  rowed  a  boat  on  a  quiet 
summer's  evening  upon  the  sea.  At  every  stroke  of  the  oar, 
a  gleam  is  sent  along  its  length.  An  analytical  study  of  this 
phenomenon  has  been  made  by  MASS  ART  ('93,  p.  62).  When 
a  drop  of  water  containing  Noctiluca  is  put  on  filter  paper,  and 
the  liquid  is  absorbed,  there  comes  a  moment  when  the  surface 
film  of  the  water  flattens  the  spherical  body  of  Noctiluca.  At 
that  moment  of  pressure  light  is  emitted.  If,  however,  the 
water  is  put  into  a  slight  vibration  by  a  needle  attached  to  a 
tuning-fork,  and  if  the  agitation  is  insufficient  to  deform  the 
body,  no  light  will  be  given  forth.  Deformation  of  the  body, 
but  not  slight  agitation,  is,  consequently,  accompanied  by  those 
metabolic  processes  which  result  in  the  production  of  light. 

Secondly,  contact  may  induce  the  production  and  discharge 
of  secretions.  VERWORN  ('89,  p.  81)  has  called  attention  to 
this  phenomenon  in  the  cases  of  Actinosphserium  and  Thalassi- 


§  2]  EFFECT   ON  METABOLISM  AXD  MOVEMENT  99 

cola.  When  Actinosphserium  is  subjected  to  a  slight  stimula- 
tion, such  as  would  be  produced  by  other  Protozoa  wandering 
among  its  pseudopodia,  it  shows  no  response.  But  when  an 
infusorian  or  a  rotifer  swims  against  the  pseudopodia  with 
force,  they  discharge  a  sticky  substance  which  holds  the  dis- 
turbing organism  fast.  The  same  result  follows  the  irritation 
of  one  of  the  pseudopodia  by  touching  it  with  a  fibre  of  cloth 
or  filter  paper.  Like  effects  follow  the  irritation  of  Thalas- 
sicola.  Thus,  some  Protista  respond  to  particular  kinds  of 
contact  by  the  excretion  of  a  sticky  substance. 

In  the  higher  animals,  also,  contact  may  call  forth  secretions  ; 
thus,  the  stolons  of  many  hydroids  secrete  a  cement  from  the 
surface  applied  to  the  substratum. 

Among  the  higher  plants,  also,  contact  has  sometimes  a  similar 
effect.  Examples  appear  in  DARWIN'S  ('75,  p.  393)  work  on 
the  gland  cells  of  insectivorous  plants.  In  many  species,  to 
be  sure,  e.g.  Drosera,  Dionsea,  Drosophylluin,  mere  contact  of 
inorganic  bodies  has  no  effect  upon  the  secretions  of  the  glands 
of  the  leaves.  In  the  case  of  Pinguicula  lusitanica,  however, 
fragments  of  glass,  as  well  as  seeds  and  albumen,  caused  the 
glands  with  which  they  came  in  contact  to  secrete  more  freely 
than  before. 

This  response  to  contact  by  secretion  is,  for  the  most  part, 
an  advantageous  one.  It  enables  the  Protista  and  the  insec- 
tivorous plants  to  hold  their  prey  or  their  enemy,  as  the  case 
may  be  ;  and  it  enables  the  stolon  to  hold  fast  to  the  sub- 
stratum. 

The  change  in  metabolism  may  be  so  profound  as  to  lead 
to  death.  HOKVAKTH  ('78)  and  MELTZER  ('94)  have  shown 
that  when  bacteria  are  violently  shaken,  not  only  is  growth 
interfered  with,  as  we  shall  see  in  the  second  part  of  this 
book,  but  death  may  ensue,  so  that  cultures  of  bacteria  may 
be  sterilized. 

We  now  turn  to  consider  the  modification  of  movement  by 
molar  agents.  The  general  phenomena  are  familiar.  An 
amoeba,  any  other  rhizopod,  or  a  white  blood  corpuscle  con- 
tracts when  the  cover-glass  over  it  is  disturbed.  The  stream- 
ing in  the  plasmodia  of  Myxomycetes  is  retarded  or  inhibited 


100 


MOLAR  AGENTS  AND  PROTOPLASM 


[Cn.  IV 


x   • 


upon  shaking.  When  alga  cells,  such  as  those  of  Chara  or 
Vallisneria,  are  freshly  transferred  to  the  slide,  the  disturbance 
causes  cessation  of  movements  (HOFMEISTER,  '67,  p.  .50). 
When  the  stamen  hairs  of  Tradescantia  are  crushed,  the  stream- 
ing of  the  plasma  ceases.  When  Chara  is  cut  across  or  punct- 
ured, rotation  stops  for  a  longer  or  shorter  time  (DUTROCHET, 
'37,  p.  780).  Even  when  a  stem  of  Chara  is  pricked  at  the 
node  by  a  needle,  without  penetrating  into  the  cavity,  move- 
ment ceases  for  a  minute 
or  two.  Thus,  mechanical 
disturbance  profoundly  af- 
fects protoplasm. 

Let  us  now  consider 
more  in  detail  the  changes 
which  take  place  in  the 
protoplasm.  VERWOKN 
('92,  p.  24)  has  given 
us  data  011  this  matter. 
Orbitolites  is  a  rhizopod 
having  extremely  deli- 
cate, filamentous  pseudo- 
podia.  If  one  of  these 
pseudopodia  be  cut  across 
as  at  #,  Fig.  13,  a,  the 
following  changes  occur : 
the  protoplasm  lying  next 
the  cut  directly  collects 
into  small  spherical  or 
fusiform  masses  which  be- 
gin to  migrate  centripe- 
tally  (Fig.  13,  5).  This  movement  meets  with  the  normal 
centrifugally  migrating  plasm  and  turns  the  latter  towards  the 
centre  again  (Fig.  13,  c).  Gradually  the  thickenings  elongate 
until,  before  they  have  reached  the  central  body,  they  are  no 
longer  visible  (Fig.  13,  d).  In  about  2  minutes  normal  move- 
ments are  completely  restored  (Fig.  13,  e).  Slightly  different 
results  are  gained  from  Cyphoderia  (Fig.  14).  When  the 
large  pseudopodium  of  this  organism  is  touched  with  a  needle 
near  its  distal  end,  it  thickens  (as  in  the  case  of  Obitolites)  and 


FIG.  13.  —  Pseudopodium  of  Orbitolites,  re- 
tracting as  a  result  of  local  stimulation. 
The  arrows  give  the  direction  of  the 
streaming  of  protoplasm.  At  the  left  is 
shown  the  beginning  of  the  excitation;  at 
the  right,  its  end.  (From  VERWORN,  '92). 


§2] 


EFFECT   OX   METABOLISM  AXD   MOVEMENT 


101 


the  thick  region,  together  with  all  the  proximal  lying  proto- 
plasm, begins  to  flow  towards  the  centre.  The  whole  plasma 
thread  retracts. 

Again,  if  an  individual  of  Difflugia  (Fig.   15)  be  slightly 
shaken,  the  pseudopodium  contracts  into  the  shell ;    if  it  be 


FIG.  14.  —  Cyphoderia  margaritacea,  showing  the  retraction  of  its  pseudopodium  as  a 
result  of  irritation  at  the  point  indicated  by  the  arrow.  (From  VERWORN,  '92.) 

FIG.  15.  —  Dimugia  urceolata :  at  a,  stimulated  by  a  weak  local  irritation ;  at  6,  by  a 
somewhat  stronger  one.  (From  VERWORX,  '89.) 

violently  shaken,  the  following  changes  occur  :  drops  of  a  less 
highly  refractive  substance  seem  to  gather  on  the  surface  of 
the  filamentous  pseudopodium  and  unite  to  form  a  sheath  sur- 
rounding a  more  highly  refractive  axis.  At  the  same  time, 
axis  and  sheath  retreat  into  the  central  mass.  In  this  case, 
then,  we  have  a  segregation  of  dissimilar  protoplasmic  sub- 
stances, and  a  tendency  to  collect  about  centres  along  the 


102 


MOLAR  AGENTS  AND  PROTOPLASM 


[Cii.  IV 


FIG.  16.  — A  series  showing  seven  phases  in  the  contraction  of  a  pseudopodium  of 
Difflugia  lobostoma,  following  total  stimulation.  The  series  passes  from  left 
to  right.  (From  VERWORN,  '92.) 

pseudopodium  and  in  the  whole  mass.     The  same  thing  is  seen 
in  the  widely  dissimilar  Actinospherium  (Fig.  17).     Here  is 


Fia.  17.  —  Actinosphaermm  Eichhornii,  unirritated.     Natural  size  about  0.5  mm. 
(From  VEBWORN,  '89.) 

especially  noticeable  (Figs.  18,  19)  the  tendency  to  produce 
fusiform  or  spherical  aggregations,  and  to  retract  the  pseudo- 
podia.  So,  too,  in  the  irritated  stamen  hairs  of  Tradescantia ; 


2]  EFFECT   ON  METABOLISM   AND  MOVEMENT  103 


FIG.  18.  —  Actinosphaerium  Eichhornii,  at  the  beginning  of  irritation.  The  proto- 
plasm is  accumulated  along  the  pseudopodia  in  drops  and  spindles.  (From 
VERWORN,  '89.) 

says  HOFMEISTER  ('67,  p.  50),  "The  threads  become  knotty, 
tear  apart,  draw  together  into  short  clubs  or  balls,  and  fuse 


FIG.  19.  —  Three  pseudopodia  of  the  same  individual,  much  enlarged,  a,  normal 
condition;  the  axial  thread  is  seen,  surrounded  by  protoplasm.  6,  the  pseudo- 
podia at  the  beginning  of  stimulation,  c,  d,  the  stimulation  is  continuing,  and 
the  axial  thread  is  shortening,  e,  the  three  pseudopodia  are  almost  completely 
retracted.  (From  VERWORN,  '89.) 

partly  with  the  collection  of  protoplasm  lying  about  the  cell- 
nucleus  and  partly  with  the  peripheral  protoplasmic  layer." 

These  similar  phenomena  from  various  organisms  are  funda- 
mental ;    how  are  they  to  be  interpreted?     It  is  well  known 


104  MOLAR  AGENTS   AND  PROTOPLASM  [Cii.  IV 

that  non-vital  semi-fluid  substances  tend  to  assume  a  spherical 
form  by  virtue  of  the  property  of  surface  tensions.  That  pro- 
toplasm does  not  always  assume  this  form  is  due  to  special 
causes.  When  a  Protist  or  one  of  its  pseudopodia  is  irritated 
by  contact,  it  tends  to  assume  a  spherical  form  or  a  thread  tends 
to  aggregate  into  spherical  drops.  It  seems  probable,  we  can- 
not say  more  than  that,  that  this  aggregation  is  due  to  a  dimi- 
nution in  the  activity  of  those  causes  which  oppose  the  action 
of  surface  tension;  and  so  the  latter  reasserts  itself.  It  is 
likewise  possible  that  new  attractive  centres  arise.  That  a 
thread  should  break  up  into  drops  indicates,  moreover,  a  loss 
in  cohesion.  Loss  of  cohesion,  formation  of  new  centres  of 
attraction,  arid  diminution  of  the  form-maintaining  forces,  — 
these  seem  to  be  the  effects  of  contact.  They  must  be  due  to 
the  chemical  changes  wrought  by  contact. 

The  changes  just  referred  to  constitute  the  essence  of  con- 
traction, a  phenomenon  of  widespread  occurrence  not  only  among 
Protista,  but  among  the  higher  plants  and  animals  ;  for  ex- 
ample, in  the  sensitive  plant  and  in  Vertebrate  muscle.  Into 
these  contraction  phenomena  which  follow  contact  in  the  higher 
organisms  we  cannot  go  ;  their  study  belongs  to  the  field  of 
plant  and  animal  physiology.  At  bottom,  however,  we  must 
believe  many  of  these  phenomena  in  the  higher  organisms  to 
be  due  to  the  same  causes  as  contraction  in  Protista. 

A  few  words  concerning  rhythmically  repeated  disturbances. 
A  single  disturbance  gives  rise,  as  we  have  seen,  to  a  series  of 
phenomena  producing  contraction;  but  in  a  few  seconds  the 
effects  of  the  disturbances  are  past  and  the  protoplasm  returns 
to  its  uncontracted  form.  If,  however,  the  shock  is  repeated 
before  relaxation  has  fully  occurred  a  new  contraction  is  super- 
imposed on  the  first,  and  the  resulting  contraction  is  more 
violent  than  a  single  one.  If  now  shock  follow  shock  in  quick 
succession,  a  violently  contracted  condition,  known  as  tetanus, 
results.  Under  the  condition  of  tetanus  the  amoeba  becomes  a 
spherical  mass,  Actinosphserium  retracts  all  of  its  pseudopodia, 
a  branching  Carchesium  stock  forms  a  little  ball,  and  muscle 
fibres  are  greatly  shortened.  In  a  word,  rhythmically  repeated 
shocks  are  accompanied  by  an  exaggeration  of  those  changes 
which  result  from  a  single  shock. 


§  3]  THIGMOTAXIS  105 

§  3.  EFFECT  OF  MOLAR  AGENTS  IN  DETERMINING  THE 
DIRECTION  OF  LOCOMOTION  —  THIGMOTAXIS  (STEREOTAXIS) 
AND  RHEOTAXIS  * 

We  have  already  seen  that  when  a  pseudopodium  of  an 
amoeba  is  touched  by  a  solid  body  it  retracts.  In  this  retrac- 
tion the  centre  of  mass  is  transferred  to  a  new  point.  If  the 
stimulation  is  often  repeated  upon  the  same  side,  contraction 
continues  on  that  side,  until  eventually  the  amoeba  will  have 
migrated  a  considerable  distance.  In  this  case  the  determina- 
tion of  the  direction  of  locomotion  is  closely  allied  to  the  phe- 
nomena of  contraction  as  a  result  of  stimulation,  considered  in 
section  2.  The  retraction  of  the  protoplasm  which  follows  its 
irritation  is  the  cause  of  the  migration  of  the  amoeba  in  a  defi- 
nite direction.  This  direction  is  away  from  the  touching  body. 
The  response  may  consequently  be  called  negative  thigmo  taxis. 

The  phenomenon  of  negative  thigmotaxis  is  widespread. 
There  are  almost  no  free-moving  organisms  which  do  not  move 
away  from  contact  or  molar  disturbance  of  an  unusual  or  vio- 
lent sort.  Thus  you  may  very  definitely  control  the  direction 
of  movement  of  a  planarian  or  a  slug  by  touching  the  body 
upon  the  side  opposite  the  direction  in  which  you  wish  it  to 
move.  In  such  cases,  also,  there  is  first  a  contraction  of  the 
body  upon  the  irritated  side. 

The  opposite  phenomenon  of  movement  towards,  or  clinging 
to,  the  irritating  body  —  positive  thigmotaxis  '  —  is  less  common 
and  therefore  more  striking.  It  has  long  been  known,  I  imag- 
ine, —  it  certainly  is  an  observation  easily  made,  —  that  an 
amoeba  which  has  come  in  contact  with  a  solid  body  clings 
close  to  it  and  moves  over  its  surface.  LE  DANTEC  ('95, 
p.  211)  has  described  the  action  in  much  detail.  An  amoeba 
descending  in  the  drop  touches  the  glass  slide  first  by  a  single 
protruding  pseudopodium.  Xext,  the  pseudopod  elongates  hori- 
zontally, and  at  the  same  time  affixation  takes  place,  so  that  the 
organism  does  not  roll  about  when  the  water  is  agitated.  The 


*  Thigmotaxis,  under  the  different  form  "  thigmotropism  "  (from 
"contact")  was  first  applied  to  these  phenomena  by  VEKWORN  ('89,  p.  90); 
stereotaxis,  under  the  form  "  stereotropism  "  (from  o-repeos,  "solid"),  was  intro- 
duced by  LOEB  ('90,  p.  28),  and  is  practically  synonymous  with  thigmotaxis. 


106        MOLAR  AGENTS  AND  PROTOPLASM      [Cn.  IV 

pseudopod  gradually  extends  itself,  and  new  ones  are  formed, 
until  at  last  the  whole  substance  of  the  amosba  is  spread  out 
parallel  to  the  glass,  over  whose  surface  it  moves.  That  there 
is  a  considerable  adherence  is  shown  by  the  fact  that  the 
amoeba  is  not  disturbed  by  an  appreciable  current.  If,  how- 
ever, it  is  made  to  contract,  it  looses  its  hold  at  once. 

Very  similar  phenomena  occur,  according  to  VERWORN  ('95, 
p.  429),  in  Orbitolites  also.  Such  an  organism  lying  in  a  watch 
glass  begins  to  send  out  pseudopodia  which,  so  long  as  they 
move  free  in  the  water,  are  simple  straight  threads  ;  but  when 
they  touch  the  glass  they  adhere  to  it,  stream  out  along  it,  and 
send  out  branches.  In  these  Rhizopoda,  consequently,  the 
presence  of  a  solid  body  is  a  stimulus  to  the  spreading  out  of 
the  pseudopodia  and  to  those  changes  by  which  close  adhesion 
is  effected. 

We  now  pass  to  the  other  simple  organisms.  Among  Infu- 
soria, PFEFFER  ('88,  pp.  618-621)  has  found  that  Glaucoma 
scintillans  and,  to  a  less  degree,  Colpidium  colpoda,  Parame- 
cium  aurelia,  and  Stylonychia  mytilus  aggregate  about  solid 
bodies  in  the  water,  such  as  fragments  of  soaked  filter  paper 
or  particles  of  barium  sulphate.  Since  these  cannot  supply 
oxygen  or  soluble  substances,  the  effect  produced  is  doubtless 
due  to  contact. 

The  aggregated  organisms  tend,  in  moving,  to  keep  upon  the 
surface  of  the  solid.  Thus  PFEFFER  ('88,  p.  619)  found  that 
Urostyla  weissii,  coming  in  contact  with  glass  threads,  moved 
along  them  on  their  ventral  surfaces ;  and  MASSART  ('91) 
observed  some  Chlamydomonades  remain  hanging  to  objects 
with  which  they  came  in  contact.  VERWORN  ('95,  p.  431), 
likewise,  finds  that  Oxytricha  travels  over  the  surface  of  Ano- 
donta  eggs  or  particles  of  detritus  which  it  happens  upon  in 
the  water.  In  one  instance,  the  organism  ran  for  some  time 
over  the  surface  of  an  egg  of  Anodonta  without  being  able  to 
leave  it.  After  four  hours,  it  was  able,  by  the  aid  of  a  piece 
of  slime  which  came  in  contact  with  the  egg,  to  free  itself  from 
that  body. 

Phenomena  similar  to  the  above-described  for  bacteria  and 
Infusoria  are  found  in  spermatozoa  also.  DEWITZ  ('85  and 
'86)  first  noticed  this  in  the  case  of  the  cockroach,  Periplaneta 


§3] 


THIGMOTAXIS 


10T 


orientalis.  When  an  0.8%  or  0.9%  NaCl  solution  contain- 
ing spermatozoa  was  put  under  a  cover-glass,  the  spermatozoa 
arranged  themselves  in  two  layers,  one  in  contact  with  the 
cover-glass,  the  other  in  contact  with  the  slide.  By  isolating 
some  of  the  spermatozoa  at  the  upper  surface  and  putting  them 
under  a  cover-glass,  he  found  that  they  likewise  distributed 
themselves  at  both  upper  and  lower  surfaces.  Hence  the  segre- 
gation into  two  layers  was  not  due  to  a  difference  in  kind 
between  the  spermatozoa  occupying  the  two  positions,  but  to 
the  fact  that  there  were  here  two  surfaces  of  contact,  separated 


FIG.  20.  —  A,  Oxytricha  seen  from  below;  B,  from  the  side;  C,  crawling  over  the 
egg  of  Anodonta.     (From  VERWORN,  '95.) 

by  a  water-film.  If  a  spherical  grain  be  placed  in  the  drop  of 
water,  aggregation  takes  place  about  that  also.  A  similar 
experiment,  with  similar  results,  was  made  by  MASSART  ('88) 
with  frog  spermatozoa.  Here,  too,  the  active  spermatozoa  kept 
in  contact  with  the  upper  and  lower  glass  surfaces,  whilst  the 
weak  forms  lay  midway  between.  The  fact  that  only  active 
spermatozoa  show  this  tendency  to  keep  in  contact  with  solids, 
indicates  that  we  are  here  dealing  with  irritability  to  contact. 

The  quality  of  the  surface  influences  its  capacity  for  stimu- 
lating to  positive  thigmotaxis.  Thus,  while  mere  roughness 
has  no  effect,  if  the  surface  of  glass  be  smeared  with  a  slimy 
mass,  so  thick  that  the  spermatozoa  can  hardly  penetrate  it, 


108        MOLAR  AGENTS  AND  PROTOPLASM     [Cn.  IV 

they  may  no  longer  cling  to  the  glass,  but  wander,  undirected, 
through  the  water.  Again,  while  the  surface  film  of  water 
often  acts  thigmotactically,  if  the  surface  tension  is  reduced 
by  a  thin  covering  of  oil,  it  no  longer  holds  the  organisms. 
It  would  seem  that  a  certain  minimum  difference  in  rigidity, 
between  any  surface  and  the  medium,  is  necessary  in  order 
that  the  surface  should  act  thigmotactically. 

Once  in  contact  with  a  sufficiently  attracting  surface,  the 
organism  may  move  to  and  fro  over  it,  but  it  can  hardly  leave 
it.  It  is,  as  DEWITZ  ('86,  p.  366)  says,  as  though  the  sperma- 
tozoa were  attracted  by  a  magnet.  This  close  adhesion  of  the 
organism  to  the  irritating  surface  is  a  remarkable  phenomenon. 
LE  DANTEC  ('95)  suggests  that  the  amoeba  adheres  to  the 
glass  by  molecular  attraction.  On  the  other  hand,  it  may  be 
doubted  whether  the  close  adhesion  signifies  anything  else 
than  the  absence  of  a  sufficient  stimulus  to  leave  the  surface 
of  contact. 

When  an  organism  has  been  stimulated  by  contact  for  some 
time,  it  at  last  becomes  changed  so  that  it  no  longer  responds 
as  it  did  at  first.  Thus  Dr.  W.  E.  CASTLE  has  informed  me 
that  he  has  seen  a  colony  of  Stentors,  in  an  aquarium,  being 
constantly  struck  by  Tubifex  waving  back  and  forth,  yet  the 
Stentors  did  not  contract  as  they  usually  do  when  struck. 
PFEFFER,  ('88,  p.  619)  has  observed  that  Urostyla  retreats, 
after  a  time,  from  the  surface  with  which  it  was  in  contact. 
These  facts  indicate  that  protoplasm  can  become  acclimatized 
to  contact  so  as  to  be  no  longer  stimulated  by  it. 

We  now  turn  to  the  consideration  of  Rheotaxis,  which  may 
be  regarded  provisionally  as  a  form  of  thigmotaxis,  although 
the  possibility  of  its  being  rather  a  case  of  chemotaxis  is  not 
excluded. 

ROSANOFF  ('68)  was  the  first  to  notice  the  rheotaxis  of  the 
large  plasmodium  of  ^Ethalium  septicum,  but  he  ascribed  it 
to  geotaxis.  The  correct  interpretation  was  first  given  by 
STRASBURGER  ('78,  p.  62),  and  has  been  confirmed  by  JONX- 
SON  ('83),  and  STAHL  ('84).  When  ^Ethalium  is  placed  on  a 
strip  of  saturated  filter  paper,  the  upper  end  of  which  is 
dipped  in  a  beaker  of  water,  it  is  subjected  to  a  current 
of  water  in  the  substratum.  At  the  same  time  it  moves 


§  3]  RHEOTAXIS  109 

against  the  current.      The  current  controls  the  direction  of 
locomotion. 

The  evidence  that  it  is  indeed  the  current  is  partly  gained 
by  exclusion.  It  cannot  be  geotaxis,  for  if  the  current  is 
flowing  upwards  on  any  arm  of  the  strip,  the  plasmodium 
flows  down.  It  can  hardly  be  hydrotaxis,  for  the  strip  is  uni- 
formly saturated  throughout.  The  action  of  light  may  be 
excluded  by  shutting  the  whole  apparatus  in  the  dark,  when 
the  same  response  occurs.  When  the  direction  of  the  current 
in  the  strip  is  reversed,  the  movement  of  the  plasmodium  is 
reversed  also.  Thus  no  other  cause  will  explain  the  result  but 
that  of  the  moving  water. 

Satisfactory  evidence  that  it  is  the  current  as  such  which  acts 
will  not  be  forthcoming  until  it  has  been  shown  that  other 
fluids  than  water,  e.g.  oil,  provoke  a  similar  response.  Until 
such  an  explanation  has  been  tried,  it  must  remain  uncertain 
whether  the  phenomenon  is  not  perhaps  due  to  a  difference  in 
the  quality  of  the  afferent  and  the  efferent  water. 

Finally,  it  must  be  mentioned  that  higher  organisms,  espe- 
cially fish,  are  rheotactic.  Whoever  has  seen  fish  ascending 
streams  from  the  sea  in  the  spring  has  had  this  vividly 
impressed  upon  him.  Before  some  dam  thousands  of  fish  will 
be  seen,  all  facing  the  torrent  of  water  against  which  they  can 
hardly  hold  their  own.  It  is  the  current  which  determines 
their  position.  They  are  responding  to  the  direction  of  flow 
of  the  waters. 

To  recapitulate :  In  many  non-living  substances,  especially 
organic  compounds,  violent  chemical  changes  (explosions)  are 
brought  about  by  contact  and  especially  by  repeated  vibra- 
tions. So,  too,  in  protoplasm,  chemical  change,  exhibiting 
itself  in  modified  metabolism,  frequently  follows  contact.  The . 
explanation  adapted  to  the  non-living  series  of  phenomena  is 
adapted  to  the  living  series  also,  —  the  molecules  of  the  sub- 
stance are  complex,  loosely  associated,  very  unstable,  so  that 
even  a  slight  mechanical  disturbance  will  serve  to  dissociate 
their  atoms.  Protoplasm  is  a  mixture  of  so  many  substances 
that  the  whole  mass  does  not  become  changed  at  once ;  but 
continued  stimulation  may  eventually  produce  such  wide- 
spread changes  as  to  lead  to  death.  One  of  the  most  evident 


110        MOLAR  AGENTS  AND  PROTOPLASM      [Cn.  IV 

results  of  contact  upon  protoplasm  is  modification  of  move- 
ment,—  momentary  quiet,  followed  by  contraction.  Rapidly 
repeated  shocks  lead  to  a  summation  of  responses  called  teta- 
nus. Slowly  repeated  shocks  may  lead  to  acclimatization  to 
contact.  Finally,  the  direction  of  locomotion  is  in  some  cases 
controlled  by  contact ;  many  organisms  move  from  the  touch- 
ing body  —  negative  thigmotaxis ;  others  may  face  the  impact 
of  flowing  water  or  keep  close,  as  though  attached,  to  the  rigid 
surface  —  positive  thigmotaxis.  If  the  changed  chemical  con- 
dition following  contact  be  called  the  "response,"  then  all 
changes  wrought  by  contact  on  protoplasm  may  be  considered 
as  responses. 

LITERATURE 

CHAMPION,  P.  and  PELLET,  H.  72.     Sur  la  theorie  de  1'explosion  des  com- 
poses detonants.     Compt.  Rend.     LXXV,  210-214. 
DANTEC,  F.  LE  '95.     Sur  1'adherence  des  amibes  aux  corps  solides.     Compt. 

Rend.     CXX,  210-213.     28  Jan.  1895. 
DARWIN,  C.  75.     (See  Chapter  I,  Literature.) 
DEWITZ,  J.  '85.     Ueber  die  Vereinigung  der  Spermatozoen  mit  dem  Ei. 

Arch.  f.  d.  ges.  Physiol.     XXXVII,  219-223.     29  Oct.  1885. 
'86.     Ueber  Gesetzmassigkeit  in  der  Ortsveranderung  der  Spermatozoen 

und  in  der  Vereinigung  derselben  mit  dem  Ei.     Arch,  f .  d.  ges.  Physiol. 

XXXVIII,  358-385.     31  March,  1886. 
DUTROCHET  '37.     (See  Chapter  VIII,  Literature.) 
HOFMEISTER,  W.  '67.     Die  Lehre  von  der  Pflanzenzelle.     Leipzig:  Engel- 

mann.     664  pp.     1867. 
HORVATH,  A.  78.     Ueber  den  Einfluss  der  Ruhe  und  der  Bewegung  auf 

das  Leben.     Arch.  f.  d.  ges.  Physiol.      XVII,  125-134.      21   May, 

1878. 
JONSSON,  B.  '83.     Der  richtende  Einfluss  strb'menden  Wassers  auf  wachsende 

Pflanzen   und   Pflanzentheile    (Rheotropismus).      Ber.    D.    bot.    Ges. 

I,  512-521. 

LOEB,  J.  '90.     (See  Chapter  VII,  Literature.) 
MASSART,  J.  '88.     Sur  1'irritabilite  des   spermatozoides   de   la  grenouille. 

Bull.  1'Acad.  roy.  Belg.     (3)  XV,  750-754. 
'91.     La  sensibilite   tactile   chez   les   organismes   inferieurs.      Jour,   de 

Medecine  de  Bruxelles.    5  Jan.  1891.    [Abstract  only  seen  in  Centralb. 

f.  Bacteriol.     XI,  566.] 
'93.     (See  Chapter  I,  Literature.) 
MELTZER,  S.  J.  '94.     Ueber  die  fundamentale  Bedeutung  der  Erschiitterung 

fur  die  lebende  Materie.     Ztschr.  f.  Biol.     XXX,  464-509. 
PFEFFER,  W.  '88.     (See  Chapter  I,  Literature.) 


LITERATURE  111 

ROSAXOFF,  S.  '68.  De  I'influence  de  1'attraction  terrestre  sur  la  direction 
des  plasmodia  des  myxomycetes.  Mem.  Soc.  Sci.  nat.  Cherbourg, 
XIV,  149-172,  Tab.  I. 

STAHL,  E.  '84.     (See  Chapter  I,  Literature.) 
STRASBURGER,  E.  '78.     (See  Chapter  VII,  Literature.) 
VERWORX,  M.  '89.     (See  Chapter  I,  Literature.) 

'92.    Die  Bewegung  der  lebendigen  Substanz.     103  pp.    Jena :  Fischer. 

1892. 
'95.     Allgemeine  Physiologic.     584  pp.    Jena :  Fischer.     1895. 


CHAPTER  V 
EFFECT  OF  GRAVITY  UPON  PROTOPLASM 

WE  shall  consider  this  subject  under  three  heads :  (I)  Methods 
of  Study ;  (II)  Effect  of  Gravity  upon  the  Structure  of  Proto- 
plasm; (III)  Control  of  Locomotion  by  Gravity — Geotaxis. 

§  1.   METHODS  OF  STUDY 

Under  normal  circumstances  gravity  acts  upon  organisms 
continuously,  uniformly,  and  in  one  direction  only  at  a  time. 
In  this  respect  it  is  widely  different  from  most  of  the  agents 


FIG.  21.  —  Diagram  of  the  essential  part  of  a  klinostat.  A  rotating  block  or  drum, 
to  which  tubes  containing  the  geotactic  organisms  may  be  attached  in  the  position 
indicated. 

which  we  have  to  consider.  Since  its  action  is  uniform  it  can 
be  varied  only  in  an  indirect  way  ;  i.e.  by  turning  the  organism 
or  by  replacing  gravity  in  part  by  a  force  working  in  another 
direction.  One  of  the  simplest  ways  of  turning  the  organism 
so  as  to  eliminate  gravity  is  by  means  of  the  klinostat  (Fig.  21). 
This  is  made  in  various  forms,  and  consists  essentially  of  a 
horizontal  rod  supported  near  the  ends  and  made  to  revolve 
about  its  long  axis  by  clockwork.  Towards  the  middle  of  the 
rod,  or  at  one  end,  is  rigidly  affixed  a  block  to  which  may  be 

112 


§2]  EFFECT  OX  STRUCTURE  113 

fastened,  radially,  the  vessels  containing  the  objects  of  experi- 
mentation. When  the  rod  revolves,  all  sides  of  the  object 
are  brought  successively  and  equally  under  the  influence  of 
gravity's  pull.  By  this  means  the  directive  action  of  gravity 
is  eliminated. ) 

In  the  case  of  organisms  living  in  water,  the  effect  of  gravity 
may  be  overcome  by  the  buoyancy  of  the  medium.  It  is  clear 
that  an  organism  floating  in  a  medium  of  its  own  weight  can- 
not be  affected  by  gravity.  This  condition  can  be  brought 
about  by  increasing  the  specific  gravity  of  water  by  adding 
soluble  substances  such  as  gelatine  and  gum  arabic.  Since 
the  specific  gravity  of  the  organism  tends  gradually  to  change 
with  that  of  the  medium,  this  method  does  for  rapid  experi- 
ments only. 

In  dealing  with  larger  organisms,  which,  like  slugs,  can  keep 
affixed  to  glass  or  other  smooth  surfaces,  the  inclination  of  the 
surface  may  be  varied  from  a  vertical  position  to  a  horizontal 
one,  thus  varying  the  active  component  of  gravity.  Finally, 
gravity  may  be  replaced  by  centrifugal  force  by  rapidly  rotating 
either  about  a  horizontal  or  a  vertical  axis.  By  varying  the 
rate  of  rotation  the  centrifugal  force  will  vary,  in  accordance 

O      2 

with  the  formula,  /  =  ~     r,  in  which  r  is  the  rotating  radius 

L  ' 

(in  meters)  and  t2  the  square  of  the  time  of  a  rotation  (in 
seconds).  This  varying  centrifugal  force  will  act  exactly  in 
the  same  way  as  gravity,  only  from  the  centre  of  rotation. 


§  2.    EFFECT  OF  GRAVITY  UPON  THE  STRUCTURE  OF 
PROTOPLASM 

Very  few  observations  have  been  made  upon  this  subject, 
and  yet  indications  are  not  wanting  that  the  field  would  well 
repay  working.  Thus,  where  the  cell  contains  specifically 
heavier  and  lighter  substances  the  two  will  be  separated  by 
the  action  of  gravity.  This  occurs  in  plant  cells  in  which, 
according  to  DEHNECKE  ('80),  various  contained  bodies,  e.g. 
chlorophyll  granules  and  starch  grains,  tend  to  sink  to  the 
lower  side  of  the  cell.  This  result  is  produced  in  from  a  few 
minutes  to  several  hours.  This  effect  is  likewise  seen  in  many 


114 


GRAVITY  AND  PROTOPLASM 


[Cn.V 


ova  in  which  the  yolk  sinks  to  the  lower  pole  and  the  proto- 
plasm floats  on  top,  in  whatever  position  the  egg  may  be  held. 
This  fact  undoubtedly  has  an  important  effect  upon  develop- 
ment, as  we  shall  see  later. 

Of   the   specifically   heavier   bodies  above   referred   to,  the 
nucleolus  is  a  striking  example,  as  HERRICK  ('95)  has  recently 

shown.     Thus,  when  the 

— • ovary    of    a    lobster    is 

killed,  the  nucleoli  of 
all  the  nuclei  are  found 
in  contact  with  that  part 
of  the  nuclear  membrane 
which  was  the  lowest  at 


FIG.  22.  —  Section  through  the  ovary  of  a  lobster 
hardened  with  its  dorsal  surface  (D)  upper- 
most. The  nucleoli  lie  against  the  ventral 
surface  of  the  nucleus.  Magnified  50  diame- 
ters. (From  HERRICK,  '95.) 


FIG.  23.  —  Section  through  the 
nucleus  of  a  young  ovum 
(£  mm.  in  diameter)  showing 
the  nucleolus,  which  has,  ap- 
parently, caused  a  distention 
of  the  nuclear  membrane  by 
the  pressure  of  its  own  weight. 
Arrow  shows  the  direction  of 
the  earth's  centre.  Magnified 
248  diameters.  (From  HER- 
RICK,  '95.) 


the  moment  of  killing  (Fig.  22).  The  weight  of  the  nucleolus 
is  relatively  so  great  as  sometimes  to  cause  a  depression  in  the 
part  of  the  nuclear  membrane  upon  which  it  rests  (Fig.  23). 

§  3.   CONTROL  OF  THE  DIRECTION  OF  LOCOMOTION  BY 
GRAVITY  —  GEOTAXIS  * 

The  control  of  the  movements  of  Protista  has  been  investi- 
gated chiefly  by  four  naturalists  :  SCHWARZ  ('84),  who  studied 
Euglena  and  Chlamidomonas ;  ADERHOLD  ('88),  who  studied 


So  called  by  SCHWARZ  ('84,  p.  71). 


§  3]  GEOTAXIS  115 

Euglena  and  desmids  ;  MASSART  ('91),  who  worked  upon 
bacteria,  and  ciliate  and  flagellate  Infusoria ;  and  JENSEN  ('93), 
who  experimented  with  Euglena,  Chlamydomonas,  and  eight 
species  of  Ciliata. 

The  observation  that  led  SCHWARZ  to  his  study  was  that 
Euglena  and  Chlamidomonas,  shaken  up  with  sand  and  covered 
by  it,  constantly,  even  in  the  dark,  rose  to  the  surface.  The 
experiments  now  made  by  SCHWAKZ  to  determine  the  true 
cause  of  the  pheriornenon  were  a  model  of  experimental  investi- 
gation. In  the  first  place  only  fresh  and  actively  moving 
individuals  were  used,  and  light  was  carefully  excluded,  either 
by  enveloping  the  culture  vessel  in  black  paper,  or  by  working 
in  a  dark  chamber.  I  shall  now  give  in  detail  the  experiments 
and  their  results. 

When  the  Flagellata  were  placed  in  water  they  responded 
like  those1  in  sand  —  they  soon  came  to  the  upper  surface.  But 
may  not  this  upward  movement  be  purely  passive  due  to  the 
small  specific  gravity  of  the  algse  or  to  currents  in  the  water  ? 
To  get  an  answer  to  this  question  SCHWARZ  heated  the  sand 
to  70°  C  —  a  fatal  temperature  —  and  no  aggregation  occurred. 
Again,  the  algae  were  subjected  to  vapor  of  chloroform ;  no 
aggregation.  Again,  to  a  low  temperature  (5°  to  6°) ;  no 
aggregation.  An  aggregation  occurred,  however,  when  the 
temperature  of  the  same  culture  was  raised  to  22°.  Finally, 
Lycopodium  spores  and  Euglena  in  the  resting  stage  do  not 
move  upwards  ;  hence  no  currents  are  passing  in  this  direction. 
On  the  contrary,  these  experiments  show  that  the  upward 
movements  of  the  algae  are  the  results  of  its  own  active  loco- 
motion. 

Nor  can  it  be  that  anything  else  than  gravity  determines  the 
direction  of  the  locomotion.  That  the  greater  amount  of  oxy- 
gen at  the  upper  level  is  not  the  controlling  agent  was  shown 
by  smearing  the  sides  of  a  glass  cylinder  with  a  thin  layer  of 
sand  containing  the  algae.  In  this  thin  layer,  permeated  by 
oxygen,  they  still  accumulated  at  the  upper  margin.  That  the 
locomotion  was  not  directed  by  currents  in  the  water  (Rheo- 
taxis,  p.  108)  was  indicated  by  the  fact  that  whether  the  free 
end  of  the  tube,  at  which  evaporation  is  occurring,  be  up  or 
down,  migration  is  always  upwards.  Thus,  since  the  stimulus 


116  GRAVITY   AND  PROTOPLASM  [Cii.  V 

of  chemical  agents  and  currents  was  eliminated,  gravity  seemed 
to  remain  as  the  only  directing  force. 

It  only  remained  to  show  that  the  attractive  force  of  the 
earth  can  be  replaced  by  centrifugal  force,  and  this  SCHWARZ 
was  able  to  do  by  means  of  the  klinostat.  By  varying  the 
rate  of  rotation  of  this  machine  he  varied  the  centrifugal  force 
and  was  able  to  determine  the  limits  within  which  the  Infusoria 
move  against  an  opposing  force.  The  acceleration  of  the  rota- 
tion-force may  be  expressed  in  terms  of  the  attraction  of  gravity 

as  a  unit  by  the  formula  c  =  -,  when  c  equals  the  acceleration 

y 

of  centrifugal  force  in  the  required  units ;  /",  the  centrifugal 
force  found,  as  on  p.  113 ;  and  g  the  acceleration  due  to  gravity. 
,  It  appeared  from  the  experiments  that,  in  both  living  Euglena 
and  Chlamidomonas  migration  took  place  towards  the  central 
end,  thus  against  the  centrifugal  force,  when  the  latter  was 
over  0.5  g.,  and  under  8.5  g.  Under  the  lower  limit  no  migra- 
tion occurred ;  near  the  upper  limit  aggregation  occurred  at 
both  ends ;  above  the  upper  limit  aggregation  took  place  at  the 
peripheral  end  —  that  is  to  say,  with  the  centrifugal  force. 
Clearly,  then,  geotaxis  is  in  these  cases  a  movement  against  an 
opposing  force,  provided  that  force  is  considerable  (over  0.5  g.) 
but  not  too  great  (over  8.5  g.). 

The  workers  in  this  field  who  followed  SCHWARZ  advanced 
our  knowledge  of  geotaxis  in  two  principal  ways :  first,  by 
increasing  the  number  of  organisms  known  to  be  geotactic,  and, 
secondly,  by  revealing  the  fact  that  closely  allied  species  may 
have  geotaxis  of  opposite  sense. 

MASSART  ('91,  pp.  161—167)  employed  a  simple  but  satisfac- 
tory method.  He  placed  Protista  in  a  capillary  tube  which  was 
open,  hence  equally  oxygenated  at  the  two  ends.  By  invert- 
ing the  tube  the  ends  were  brought  into  different  relative  posi- 
tions with  respect  to  the  earth,  causing  the  geotactic  organisms 
to  migrate  throughout  its  length.  As  a  result  of  his  experi- 
ments it  appeared  that  Spirillum;  the  flagellata,  Polytoma, 
Chlamydomonas,  and  Chromulina ;  and  the  ciliata,  Anophrys 
and  Euplotes,  are  geotactic^  The  sense  of  geotaxis  may  be 
different  between  individuals  of  the  same  genus ;  thus,  under 
similar  conditions  Spirillum  separated  into  a  lot  lying  at  the 


3] 


GEOTAXIS 


117 


upper  part  of  the  tube  and  a  lot  at  the  lower  part ;  and  the 
individuals  of  both  the  upper  and  lower  lot  were  active.  The 
sense  of  response  depends  upon  temperature  also.  Thus  Chro- 
mtilina  woroniniana  is  negatively  geotactic  at  15°  to  20°  C., 
and  positively  geotactic  at  5°  to  7°  C.  The  other  species  men- 
tioned above  are  negatively  geotactic  —  i.e.  move  in  the  direc- 
tion opposite  to  that  in  which  the 
force  tends  to  carry  them. 

JEXSEX*  ('93)  finally  has  greatly 
extended  our  knowledge  of  the  spe- 
cies responsive  to  gravity,  has  shown 
the  necessity  for  regarding  carefully 
the  other  agents  acting  during  the 
experiment,  and  has  entered  more 
carefully  into  the  cause  of  the  phe- 
nomenon than  previous  authors.  \The 
new  forms  which  JEXSEX  worked 
with  were  these  Ciliata :  Paramecium, 
Urostyla,  Spirostomum,  Colpoda,  Col-  ^  ^.-GlaJtubes,  about  0.5 
pidium,  Ophryoglena,  and  Coleps ; 
also  the  more  commonly  used  species, 
Euglena  and  Chlamydomonas.  The 
other  agents  whose  action  may  mod- 
ify that  of  gravity  are  chemical  stuffs, 
density,  warmth,  light,  etc.  Light 
may  be  easily  excluded.  yOn  warm 
days  the  typical  geotactic  phenomena 
are  often  absent,  the  Paramecia  sink- 
ing to  the  deeper,  cooler  layers.  The 
Infusoria  aggregate  around  bacteria 
in  the  water,  —  chemotaxis  (Fig.  24, 

&),  —  and  they  shun  the  uppermost  layer,  apparently  because, 
owing  to  evaporation,  this  layer  is  denser  —  tonotaxis  (Fig. 
24,  <?).  Whether  light  inhibits  the  geotactic  response  was 
one  of  the  questions  asked  and  answered  by  JENSEN.  When 

*  JENSEN  used  glass  tubes  of  0.5  to  1  cm.  diameter,  and  5  to  100  cm.  length, 
fused  at  one  end.  To  prevent  the  free  end  becoming  richer  in  oxygen,  a  layer 
of  oil  2  to  3  cm.  high  was  poured  over  that  end,  or,  air  being  carefully  excluded, 
it  was  sealed  by  an  impermeable  plug  of  wax. 


cm.  in  diameter  and  20  cm. 
long,  fused  at  one  end,  and 
filled  with  water  containing 
Paramecium  ( represented 
by  points) .  a  shows  aggre- 
gation of  the  Paramecium 
at  upper  end  of  tube:  6, 
aggregation  of  Paramecium 
around  bacteria  suspended 
in  the  water  —  chemotaxis 
veiling  geotaxis ;  c  shows 
that  occasionally  the  Para- 
mecia avoid  the  uppermost 
layer  of  the  water.  (From 
JENSEN,  '93.) 


118  GRAVITY  AXD   PROTOPLASM  [Cn.  V 

the  centrifugal  machine  was  used  in  the  sunlight,  movements 
towards  the  centre  clearly  appeared.  It  was  thus  proved 
that  negative  geotaxis  (which  is  the  same  as  centrotaxis)  may 
occur  in  the  sunlight?\ 

(The  data  of  geotaxis  are  incomplete  without  a  consideration 
of  this  phenomenon  in  the  higher  animals.  LOEB  is  one  of  the 
first  investigators  in  this  field.  In  1888,  he  found  that  flies, 
deprived  on  both  sides  of  the  free  ends  of  the  balancers  or  the 
wings,  and  placed  upon  a  board,  move  always  upwards  upon  it. 
If  the  plane  of  the  board  is  held  oblique  to  the  horizontal,  the 
fly  always  moves  along  that  line  which  makes  the  smallest 
angle  with*  the  vertical.  Likewise  cockroaches  seem  to  be 
stimulated  by  gravity  when  this  acts  perpendicularly  to  their 
ventral  surface,  so  that  they  tend  to  move  off  from  a  horizontal 
surface  and  do  not  come  to  rest  until  they  are  on  a  more  or  less 
nearly  vertical  one?^  Thus,  LOEB  put  twenty-one  cockroaches 
into  a  truncated,  pyramidal  box,  one  of  whose  sides  made  an 
angle  of  80°  with  the  horizontal ;  another  60°,  the  third  45°, 
and  the  fourth  25°.  After  an  hour,  the  number  of  individuals 
on  each  face  of  the  box  was  counted  at  intervals  of  10  minutes. 
Adding  together  the  results  of  10  such  counts  he  found  on  the 
steepest  wall  94  cases ;  on  the  wall  inclined  at  60°,  61  cases  ; 
on  that  inclined  at  45°,  28  cases  ;  on  that  at  25°,  25  cases  ;  and 
on  the  horizontal  surfaces,  2.  After  several  hours  75  to  80% 
of  the  animals  were  found  on  the  steepest  side,  although  it  had 
the  smallest  area.  (Later,  LOEB  ('90  and  '91)  showed  that  the 
holothurian  Cucumaria  cucumis,  the  starfish  Asterina  gibbosa, 
and  the  lady-bird  beetles  (Coccinellidae)  are  likewise  geotactic. 
Finally,  it  may  be  mentioned  that  several  species  of  the  slug, 
Limax,  are  geotactic^ 

(jThere  is  in  Protista,  as  already  mentioned,  a  limit  to  the 
intensity  of  the  attractive  force  below  which  no  response  will 
occur.  Is  there  such  a  limit  in  Metazoa  likewise  ?\  Experi- 
ments upon  this  point  have  been  made  by  Miss  HELEN  PER- 
KINS and  myself  in  connection  with  my  experimental  course  at 
Radcliffe  College.  We  have  also  been  able  to  answer  the  ques- 
tion, what  difference  in  effect  is  produced  by  different  intensi- 
ties of  gravity's  action.  (We  experimented  with  the  great  slug, 
Limax  maximus,  which  crawls  readily  upon  a  glass  plate  placed 


§3] 


GEOTAXIS 


119 


So' 


40 ; 


BO* 


80* 


>0; 


at  any  angle!    As  explained  on  p.  113,  the  intensity  of  gravity's 

action  will  diminish  as  the  sine  of  the  angle  of  inclination  of 

the  plate  is  diminished  from  90°  to  0°.     We  determined  the 

deviation    of    the    slug 

from  a  vertical  position 

upon  plates   at  various 

inclinations,    and    after 

the  lapse  of  a  constant         Oo 

time  (45  seconds^ .    The     0 

So0 

experiments  were  per-  J  * 
formed  in  a  dark  box.  £ 
The  number  of  tests  3  _0 
made  at  each  inclina-  5 
tion  was  sixty.  The  1 
time  required  to  re-  1 25° 
spond  fully  to  gravity  Q 
did  not  vary  appreci- 
ably with  the  angle  of 
inclination.  ^The  re- 
sults obtained  indicated 
that  the  deviation  of 
the  slug  from  vertical- 
ity  diminished  with  the 
cosine  of  the  angle 
made  by  the  plate/\ 
The  relation  between 
the  angular  deviation 
from  vertically  and 
the  sine  of  inclination 
of  the  glass  plate  is 
graphically  represented 
in  Fig.  25.  The  con- 
clusion from  the  ex- 
periments is  that  the 
lower  limit  of  the  sen- 
sitiveness of  Limax  to  gravity  is  extremely  small,  below 
0.13  g.,  and  that  as  the  angle  of  inclination  of  the  plate 
diminishes  the  deviation  from  45°  towards  verticality  dimin- 
ishes in  accordance  with  the  relation  :  S  =  a-  sin  0,  in  which 


90°  80°  70°  60°  50°  40"  30°  20°  10°  0° 

ANGLE  OF  INCLINATION  OF  SURFACE  TO  HORIZONTAL 

FIG.  25.  —  Curves  showing  relation  between  the 
sine  of  the  angle  of  inclination  of  a  glass  plate 
and  the  angular  position  of  a  slug  which  was 
first  placed  on  it  in  a  horizontal  position  and 
then  left  for  40  seconds  in  the  dark.  Curve  A 
is  constructed  by  drawing  ordinates  from  the 
heavy  horizontal  line,  0°-45°,  corresponding  to 
each  angle  of  inclination  of  the  surface  (laid 
off  as  abscissas) .  The  lengths  of  the  ordinates 
are  determined  by  the  number  of  degrees  of  de- 
viation of  the  axis  of  the  slug  from  45°  towards 
90°.  45°  is  taken  as  a  base,  since  it  would  be 
the  mean  angular  deviation  from  the  initial 
position  of  a  slug  crawling  undirected  upon  a 
horizontal  plate.  Curve  B  is  constructed  by 
drawing  down  from  the  base  ordinates  propor- 
tional to  the  natural  sines  of  the  different  an- 
gles of  inclination  of  the  glass  plate. 


120 


GRAVITY  AND   PROTOPLASM 


[Cn.V 


S  is  the  angular  deviation  of  the  slug  from  45°  towards  90°, 
expressed  in  degrees ;  6  is  the  angle  of  inclination  of  the  plate 
to  the  horizontal,  and  a  is  a  constant. 

\  In  inquiring  into  the  cause  of  geotaxis  in  animals  it  seems 
best  to  consider  chiefly  the  phenomenon  as  exhibited  in  Protista, 

for  in  the  higher  animals  this  capacity 
seems  bound  up  with  the  possession  of 
special  organs  of  orientation^  { In  this 
group  the  first  and  apparently  most 
important  part  played  by  gravity  is 
the  determination  of  the  axis  of  the 
individual,  which  comes  to  lie  vertical 
and  with  the  head  end  up  or  down 
according  to  the  conditions  of  the 
protoplasm.  '  After  the  positions  of 
the  axis  and  poles  are  determined,  or- 
dinary locomotion  produces  the  geo- 
tactic  phenomena.  'That  gravity  may 
determine  a  vertical  position  without 
locomotion  occurring  is  shown  in  the 
ciliate  infusorian  Spirostomum  (Fig. 
26),  which  at  times  occurs  in  large 
numbers  in  ordinary  aquaria,  sus- 
pended almost  motionless  in  mid- 
water,  having  a  distinctly  vertical 
position  and  with  the  head  end 
directed  upward.^  They  cannot  be 
said  to  be  strictly  motionless,  since 
by  carefully  attending  to  them  one 


FIG.  26.  —  Spirostomum  ambi- 
guum,  side  view,  az,  ado- 
ral  zone  of  cilia ;  o,  mouth ; 
08,  gullet;  n,  nucleus;  ck, 
contractile  canal;  cv,  con- 
tractile vacuole;  a,  anus. 
Magnified  about  120  diam- 
eters. (From  BUTSCHLI 
[BRONN'S  Thier-reicb :  Pro- 
tozoa], after  STEIN.) 


can  see  them  slowly  rising  or  falling 
or  alternately,  perhaps,  rising  and  falling  in  their  almost  im- 
perceptible movements.  Miss  JULIA  B.  PLATT,  who  has 
studied  carefully  the  movements  of  Spirostomum,  found  that 
of  78  individuals  observed  all  but  7  had  the  anterior  extrem- 
ity directed  upwards  and  the  7  exceptional  individuals  were 
all  moving  downwards.  (  It  therefore  seems  quite  certain  that 
Spirostomum  tends  in  water  to  orient  itself  with  reference  to 
gravity,  although  without  aggregating  at  the  upper  surface^ 


§  3]  GEOTAXIS  121 


To  explain  the  phenomenon  of  axis-orientation,  two  principal 
theories  have  been  advanced.  The  first  may  be  called  the 
mechanical  theory;  the  second  the  response-to-stimulus  theory  A 
The  first  theory  is  that  once  suggested  by  VERWORX  ('89,  p. 
122).  It  appeared  to  him  that  it  was  self-evident  from  purely 
physical  grounds  that,  in  complete  quiescence  of  the  flagellum, 
the  hinder  end  of  the  protist  should  be  directed  downwards, 
and  not  the  anterior  flagellum-bearing  end.  If  one  conceives 
such  an  individual  to  move  its  flagellum,  which  precedes  in 
locomotion,  it  must  move  towards  the  surface  of  the  water; 
thus  against  gravity.  \VERWORX  finds  the  stimulation  theory 
inconceivable,  since  gravity  cannot  even  be  compared  with 
stimuli.  In  falling,  the  body  of  the  protist  might  rub  against 
the  water  particles,  which  would  offer  a  stimulus,  but  this 
would  be  more  allied  to  rheotaxis~7\ 

It  might  seem  an  easy  thing  to  determine  whether  geotactic 
Protista  artificially  rendered  quiescent  (e.g.  killed  or  stupefied) 
would  stand  with  their  anterior  ends  uppermost;  but  the 
killing  is  apt  to  distort  the  form,  and  the  organisms  being 
heavier  than  water  *  fall  to  the  bottom.  Something  might  be 
gained  from  an  observation  of  how  they  fall,  but  there  is  very 
great  discordance  among  authors  upon  this  point,  probably  in 
part  due  to  difficulties  of  observation.  Thus  SCHWARZ  ('84, 
p.  68)  says  that  both  Euglena  and  Chlamidomonas  assume  all 
positions  in  falling;  MASSART  ('91,  p.  164)  finds  that  Chlamido- 
monas falls  with  flagellum  directed  upwards  and  JENSEN  ('93, 
p.  451)  declares  that  Euglena  viridis  killed  by  iodine  falls 

*  Few  determinations  seem  to  have  been  made  of  the  specific  gravity  of  living 
Protista.  JENSEN  ('93a)  attempted  to  do  this  for  Paramecia,  but  his  method  was 
bad  and  his  results  bad  likewise.  He  made  solutions  of  potassium  carbonate, 
of  varying  specific  gravity,  and  found  that  Paramecium  just  floats  in  a  solution 
whose  sp.  gr.  is  1.25.  The  difficulty  of  the  method  is  that  solutions  of  salt 
having  a  relatively  small  molecular  weight  act  so  powerfully  in  withdrawing 
water  from  the  organism  as  to  cause  it  to  shrink  and  increase  in  relative 
weight.  Miss  PLATT  has  used  solutions  of  gum  arable  whose  osmotic  action 
is  so  slight  that  organisms  live  in  it  for  hours.  In  such  solutions,  paralyzed 
but  living  Spirostoma  and  Paramecia  neither  sank  nor  rose  when  the  specific 
gravity  was  between  1.016  and  1.019  ;  so  that  it  seems  probable  that  the  specific 
gravity  of  Infusoria  lies  near  1.017.  Tadpoles  recently  hatched  and  having  a 
length  of  9.5  mm.  had  a  sp.  gr.  of  1.044,  while  those  12  mm.  long  had  a  sp.  gr. 
of  1.017. 


122  GRAVITY  AND  PROTOPLASM  [Cn.  V 

almost  without  exception  with  the  broader  flagellate  pole  down- 
wards, f Both'  from  the  fact  that  it  can  be  easily  demonstrated 
that  when  a  body  heavier  than  water  falls  in  that  medium  its 
larger  end  will  precede,  and  from  the  fact  that  JENSEN  was 
especially  careful  that  the  killed  organism  should  not  be 
deformed,  his  results  must  be  considered  the  best  established.^ 

VNow,  since  the  dead  Euglena  tends  to  sink  with  .flagellum 
downwards  whereas  the  active  Euglena  stands  flagellum 
upwards,  we  must  conclude  that  the  orientation  of  Euglena 
and  probably  other  Protista  is  not  passive  but  due  to  their 
activity  and  must  be  regarded  as  a  response  more  or  less  directly 
due  to  gravity.^ 

(But  just  how  does  gravity  act  as  a  stimulus  to  determine  the 
direction  of  orientation  of  the  body?  We  have  two  principal 
theories  to  examine.  (First,  that  of  JENSEN,  that  gravity  acts 
indirectly  on  the  organism  by  directly  causing  a  difference  in 
pressure  in  the  water  at  different  levels.  \  This  difference  in 
water  pressure,  at  various  levels,  affects  directly  the  two  poles 
of  the  organisms,  which  stand  at  different  levels,  and  the 
organism  responds  to  this  difference  in  pressure.  (Th&  second 
theory,  which  I  adopt,  is  that  the  organism,  owing  to  its  specific 
gravity  being  greater  than  the  medium,  experiences  greater 
h  resistance  (friction  -f  weight)  in  going  upwards  even  to  the 
slightest  extent  than  in  going  downwards  (friction  —  weight). 

(Another  stimulus,  which  is  probably  associated  with  this,  de- 
pends upon  the  fact  that  an  unsymmetrical  body,  heavier  than 
water,  tends  to  fall  with  its  larger  end  downf^  Those  nega- 
tively geotactic-  organisms,  which  stand  with  their  larger  end 
up,  will  be  consequently  in  a  condition  of  unstable  equilibrium; 
those  organisms  which  stand  with  their  larger  end  down  will 
be  in  stable  equilibrium.  In  the  first  case  a  deviation  from 
verticality  would  be  accompanied  by  relatively  diminished 
resistance  on  one  side  ;  in  the  second  by  relatively  increased 
resistance  on  one  side.  In  either  case,  the  distribution  of  the 
mass  of  the  animal  may  give  the  organism  the  means  of  deter- 
mining, but  not  in  a  mechanical  way,  the  position  of  its  axis. 
(The  evidence  for  the  first  theory  JENSEN  finds  especially  in 
a  fact  which  he  believes  opposes  the  second.  Negatively 
geotactic  organisms,  placed  in  an  inclined  tube,  move  towards 


GEOTAXIS 


123 


upper  side  and  then  travel  obliquely,  not  vertically,  along 
toward  the  upper  part  of  the  tube,  thus  into  strata  of  con- 
stantly diminishing  pressure.^)  If  weight  controlled  in  any  way 
their  movements,  they  should  move  vertically  as  from  1  to  2 

(Fig.  27)  until  they  meet  the  side  of  the  glass.  Then  they 
should  move  off,  as  to  3,  then  vertically  to  5,  and  so  on.  Since 
they  do  not  so  move,  gravity,  JENSEN  thinks,  cannot  be  said  to 
act  directly.  In  criticism  of  this  conclusion  it  may  be  urged 
that  it  is  without  proper  foundation,  for 
if  an  organism  whose  irritability  (in- 
stincts) would  lead  it  to  move  verti- 
cally is  mechanically  unable  to  do  so 
exactly,  it  will  do  so  as  far  as  practi- 
cable. This  observation  cannot,  there- 
fore, be  said  to  militate  against  the 
second  theory.  Finally,  there  is  this 
positive  objection  to  JENSEN'S  theory 
that  it  is  applicable  only  to  geotaxis  in 
water  animals,  and  can  therefore  be 
only  a  special  explanation  of  geotaxis. 

f  On  the  other  hand,  there  is  evidence 
which  is  opposed  to  the  first  theory  and 
favors  directly  the  second^  And  JEN- 
SEX  has  himself  contributed  some  of 
this  evidence.  He  put  Urostyla  into 
a  glass  tube  containing  a  0.5%  aque- 
ous gelatine  solution.  They  showed 
no  tendency  to  go  upwards.  At  the 
expiration  of  20  hours  many  deaths 
had  occurred,  but  some  normally  ac- 
tive individuals  were  still  at  the  lower  end  of  the  tube.  Why 
this  loss  of  geotaxis  ?  JENSEN  believes  it  due  to  the  fact  that 
the  difference  in  pressure  of  the  successive  layers  did  not 
increase  proportionally  to  the  increase  in  resistance  of  the 
solution.^  I  would  suggest  that  it  may  be  due  to  the  fact 
that  the  weight  of  the  body  of  the  Protista  is  now  relatively 
less  than  that  of  the  solution,  so  that  the  organism,  tending 
to  move  against  resistance,  comes  to  lie  at  the  bottom  of  the 
buoyant  fluid,  hence  appears  positively  geotactic. 


FIG.  27.  — Hypothetical  line 
of  migration  of  Parame- 
cium  in  an  inclined  tube, 
upon  the  assumption  that 
gravity  acts  directly  to 
determine  direction  of 
locomotion,  according  to 
the  conception  of  JENSEN. 
The  arrow  at  p  indicates 
the  direction  of  the  pull 
of  gravity;  1,  2,  3,  4,  5, 
successive  positions  occu- 
pied by  the  Paramecium. 
(From  JENSEN,  '93.) 


124  GRAVITY   AND   PROTOPLASM  [Cn.  V 

(  Geotaxis  in  the  higher  organisms,  especially  Vertebrates, 
cannot  here  be  discussed  at  length.  It  is  sufficient  to  state 
that  as  LOEB  ('91,  p.  189)  concludes,  it  is  probably  dependent 
upon  the  internal  ear.  Miss  PLATT  has,  at  my  suggestion,  sub- 
jected young  negatively  geotactic  tadpoles  to  solutions  of  gum 
arabic  of  the  same  specific  gravity  as  themselves,  and  has  found 
that  they  still  migrate  upwards.  This  result  makes  it  probable 
that  here  also  orientation  is  effected  by  the  internal  ear,  and 
hence  is  independent  of  the  action  of  gravity  upon  the  entire 
body?) 

(  Finally  must  be  mentioned,  the  phenomenon  of  acclimatiza- 
tion to  a  central  pressure,  ^his  has  been  observed  by  JENSEN 
('93,  p.  470),  who  says,  when  Paramecium  or  Urostyla  has  been 
strongly  "  centrifugated  "  towards  the  peripheral  end  of  the 
tube,  where  it  is  subjected  to  a  high  pressure,  it  shows,  when 
the  tube  is  then  placed  vertically,  a  much  livelier  geotaxis 
than  it  would  have  done  without  "  centrifugating."  Clearly 
the  temporary  action  of  the  high  pressure  has  increased  the 
irritability  to  gravity?^' 

1  To  recapitulate :  Gravity  affects  the  structure  of  protoplasm 
by  separating  the  lighter  and  heavier  substances.  It  may 
determine  the  direction  of  locomotion  by  determining  the  ver- 
ticality  of  the  axis  of  the  body.  Varying  the  intensity  of 
gravity's  attraction  diminishes  the  precision  with  which  this 
determination  takes  place.  The  determination  of  the  vertical 
position  is,  in  the  lower  organisms,  probably  due  to  difference 
in  ease  of  movement  when  going  up  and  going  downX 


LITERATURE 

ADERHOLD,  R.  '88.     (See  Chapter  I,  Literature.) 

DEHNECKE,  C.  '80.   Ueber  nicht  assimilirende  Chlorophyllkorper.  Inaug.  Diss. 

Koln.  Abstr.  in  Bot.  Ztg.    XXXVIII,  795-798.    Also  in  Bot.  Centralbl. 

I,  1537. 
HERRICK,  F.  H.  '95.     Movements  of  the  Nucleolus  through  the  Action  o-f 

Gravity.     Anat.  Anz.     X,  337-340.     8  Jan.  1895. 
JENSEN,  P.  '93.     Ueber  den  Geotropismus  niederer  Organismen.     Arch,  f . 

d.  ges.  Physiol.     LIU,  428-480.     5  Jan.  1893. 
'93a.     Die  absolute  Kraft  einer  Flimmerzelle.  Arch.  f.  d.  ges.  Physiol. 

LIV,  537-551.    24  June,  1893. 


LITERATURE  125 


LOEB,  J.  '88.     Die  Orientirung  der  Thiere  gegen  die  Schwerkraft  der  Erde. 

(Thierischer  Geotropismus.)     Sb.  Wiirzb.  Phys.-med.  Ges. 
'90.     (See  Chapter  VII,  Literature.) 
'91.     Ueber  Geotropismus  bei  Thieren.     Arch.  f.  d.  ges.  Physiol.     XLIX, 

175-189.     1891. 
MASS  ART,   J.   '91.      Recherches   sur  les   organismes   inferieurs.     III.     La 

sensibilite   a  la  gravitation.      Bull.   1'Acad.   roy.   Belg.      (3)  XXII, 

158-167.     1891. 
SCHWARZ,  F.  '84.     Der  Einfluss  der  Schwerkraft  auf  die  Bewegungsrichtung 

von  Chlamidomonas  und  Euglena.     Ber.  bot.  Ges.     II,  51-72. 
VERWORN,  M.  '89.     (See  Chapter  I,  Literature.) 


CHAPTER   VI 

EFFECT  OF  ELECTRICITY  UPON  PROTOPLASM 

IN  this  chapter  we  shall  consider  (I)  some  methods  em- 
ployed in  the  investigation  of  this  subject ;  (II)  the  effect 
of  electricity  upon  the  structure  and  general  functions  of  pro- 
toplasm ;  and  (III)  the  effect  of  electricity  in  determining 
direction  of  locomotion  —  electrotaxis. 


A 


§  1.    CONCERNING  METHODS 

While  the  phenomena  of  magnetism  and  electricity  are  closely 
allied,  their  effects  upon  protoplasm  seem  to  be  widely  dis- 
similar. Thus  no  certain  action  of  magnetism  has  hitherto 
been  observed,  but  electricity,  however  produced,  causes  nearly 
uniformly  an  effect?) 

^  Any  experimental  work  with  the  electric  current  involves 
apparatus  for  its  production,  application,  and  measurement ; 
namely,  batteries  or  other  sources  of  electricity ;  electrodes  for 
applying  the  current  to  the  organism ;  troughs  to  contain  the 
free  swimming  animals  used  for  experimentation ;  a  galvanom- 
eter for  measuring  the  current ;  a  rheochord  for  varying  the 
intensity  of  the  current ;  a  reversing  key  ;  and,  for  interrupted 
currents,  an  induction  machine  with  interrupter,  and  an  elec- 
trometer for  measuring  such  currents.  A  description  of  the 
principal  forms  of  these  instruments  and  the  methods  of  con- 
structing some  of  them  will  be  found  in  VERWORN,  '95, 
Chapter  V,  and  in  OSTWALD,  '94,  Chapter  XV. 

Since  the  works  just  named  are  easily  accessible,  it  will  be 
unnecessary  here  to  describe  these  instruments  in  detail.  A 
few  additional  suggestions,  the  result  of  my  experience,  may, 
however,  be  found  helpful.  Concerning  latteries,  first;  accumu- 
lators are  without  doubt  to  be  preferred,  where  practicable,  on 

126 


• 


1]  METHODS  127 


account  of  the  strength  and  continuance  of  their  currents.  In 
other  cases,  CLAKK  or  DANEELL  elements,  if  enough  of  them 
are  united  in  series,  will  meet  the  requirements.  The  character 
of  the  electrodes,  next,  will  depend  upon  the  nature  of  the  in- 
vestigation. Xonpolarizable  ones  of  hair  (camel's-hair  brush), 
clay,  or  paper  (plug  of  filter  paper  in  glass  tubing  drawn  out 
to  a  cone)  are  usually  employed,  but  all  of  these  offer  consider- 
able resistance.  The  troughs  will  vary  in  form  and  size  with 
the  organisms  to  be  contained  in  them ;  some  of  them  will  be 
described  in  connection  with  the  experiments  in  which  they  have 
been  employed.  (They  are  all  rectangular  enclosures  having 
clay  ends  when  it  is  desirable  that  these  should  be  nonpolariz- 
able^j  /For  large  troughs,  sheet-zinc  electrodes  are  used,  cover- 
ing the  smaller  sides  of  the  trough.)  Although  some  of  the 
reflecting  galvanometers  are  more  sensitive,  a  "  millammeter " 
such  as  that  made  by  the  WESTON  Electrical  Works  is  a  much 
more  convenient  instrument  and  sensitive  enough  for  most 
work  of  this  sort.  The  rheochord  is  practically  a  low-resistance 
box,  capable  of  indefinitely  fine  gradations.  This  is  introduced 
into  the  short  branch  of  a  divided  circuit,  so  that  by  varying 
its  resistance  a  varying  share  of  the  current  shall  be  forced  into 
the  longer  circuit.  A  very  simple  and  excellent  device  for 
altering  the  strength  of  current  is  the  "  Compression-rheostat  n 
of  BLASIUS  and  SCHWEIZER  ('93).  This  consists  of  a  piece  of 
rubber  tubing  filled  with  zinc  sulphate,  stopped  at  the  ends 
and  introduced  into  the  circuit.  By  means  of  a  thumbscrew 
the  walls  of  the  middle  of  the  tube  may  be  pressed  together,  the 
lumen  correspondingly  reduced,  and  the  resistance  increased. 
The  induction  apparatus  usually  employed  is  one  invented  by 
DU  BoiS-REYMOND.  In  this  the  secondary  coil  may  be  with- 
drawn from  the  primary  coil  to  any  desired  distance,  thereby 
diminishing  the  intensity  of  the  induced  current.  Through 
the  action  of  such  an  instrument  the  current  is  alternately 
made  and  broken,  and  each  electrode  becomes  in  quick  suc- 
cession anode  and  kathode.  Since  alternating  currents  cannot 
be  measured  by  an  ordinary  galvanometer,  an  electrometer 
must  be  employed.  So  much  concerning  apparatus. 

'  A  word  should  be  said  about  the  method  of  stating  the  cur- 
rent employed?)     Very  many  authors  have  been  satisfied  with 


128  ELECTRICITY  AND  PROTOPLASM  [Cn.  VI 

saying  that  the  current  was  strong  or  weak,  others  have  given 
the  kind  and  number  of  elements  employed.  Such  statements 
are  wholly  inadequate  to  give  an  accurate  idea  of  the  strength 
of  current  to  which  the  organisms  under  experimentation  were 
subjected.  (Even  merely  to  state  the  galvanometer  reading  in 
milliamperes  is  insufficient^  We  must  know  as  nearly  as  pos- 
sible what  strength  of  current  is  passing  through  the  organism, 
and  this  involves  knowing  the  density  of  the  current  passing 
through  the  water  in  the  trough.  Now  it  is  obvious  that  a 
current  passing  through  a  mass  of  water  of  small  cross-section 
is  stronger  per  square  millimeter  than  an  equal  current  dis- 
tributed over  a  large  cross-section.  It  is  necessary,  conse- 
quently, to  know  the  cross-section  of  the  mass  of  water  through 
which  the  stimulating  current  is  passing,  in  order  to  determine 
the  "  density "  or  strength  at  any  point.  For  technical  pur- 
poses the  unit  of  current-density  is  taken  at  1  ampere  to  the 
square  millimeter.  HERMANN  and  MATTHIAS  ('94,  p.  394) 
propose  for  physiological  purposes  a  unit  one-millionth  as  great, 
to  be  designated  as  S.  &  then  indicates  a  current  of  yoVo  milli- 
ampere  per  square  millimeter  of  cross-section.  It  is  very  de- 
sirable that,  when  practicable,  currents  should  hereafter  be 
expressed  in  8's.  More  than  one  useless  discussion  has  been 
precipitated  by  not  giving  a  sufficiently  accurate  quantitative 
expression  to  the  current  employed.  (See,  for  illustration, 
below,  p.  149.) 

Finally,  the  strength  of  current  necessary  to  produce  a 
certain  result  depends  upon  the  relative  conductivity  of  the 
organism  and  the  surrounding  water.  If,  through  the  presence 
of  substances  in  solution,  the  conductivity  of  the  water  is 
abnormally  great,  one  must  use  a  greater  current  (as  read  off 
from  the  -galvanometer)  than  otherwise  to  produce  a  certain 
effect.  (WALLER,  '95,  p.  97.)  It  would  probably  be  best, 
when  possible,  to  use  in  the  trough  the  water  in  which 
the  organism  has  been  living,  since  the  quantity  of  salts 
in  the  organism  has  been  shown  to  vary  with  that  of  its 
medium.  (See  p.  88.)* 


*  See  KAISER,  Wien  Akad.  CIV,  p.  17,  1895,  for  a  new  trough  adapted  to  the 
stage  of  the  microscope. 


]  EFFECT   ON  STRUCTURE   AND  FUNCTIONS  129 


§  2.    THE  EFFECT  OF  ELECTRICITY  UPON  THE  STRUCTURE 
AND  GENERAL  FUNCTIONS  OF  PROTOPLASM 

The  fundamental  phenomenon  of  the  action  of  an  electric 
current  upon  protoplasm  may  be  seen  while  watching  a  helio- 
zoaii  (Actinosphaeriuni),  lying  in  a  drop  of  water,  through 
which  a  weak,  constant  current  is  "made."  We  find  that  the 
filamentous  pseudopodia  begin  quickly  to  retract  at  the  two 
poles  lying  in  the  axis  of  the  current ;  and  as  the  current 
continues,  this  contraction  continues  likewise.  The  primary 
effect  of  a  weak  constant  current  is  thus  a  centripetal  flowing 
of  the  protoplasm.  The  current  stimulates  to  contraction. 

If,  now,  the  current  be  increased,  or  be  longer  continued, 
further  changes  occur.  The  pseudopodia  lying  in  the  current 
become  varicose,  and  break  up  into  a  chain  of  drops;  the 
vacuoles  on  the  periphery  begin  to  burst,  emptying  out  their 
fluids;  and  in  these  regions  the  protoplasm  collapses.  Thus, 
the  stronger  current  produces  continued  contraction,  accom- 
panied by  collapse  of  the  protoplasmic  foam-work. 

Finally,  the  plasma  itself  begins,  upon  the  anode  side,  to  dis- 
integrate, and  the  loose  particles  to  move  towards  the  positive 
electrode.  As  the  plasma  of  this  side  is  gradually  eaten  away, 
the  outline  of  the  Actinosphserium  passes  through  phases  like 
those  of  the  waning  moon,  until,  finally,  the  last  thin  crescent 
fades  away.  The  particles  of  the  mass  have  wholly  lost  their 
cohesion  (Fig.  28). 

The  facts  just  given  concerning  the  behavior  of  Actino- 
sphaerium  to  the  constant  current  are  gathered  from  the  observa- 
tions of  KUHNE  ('64,  p.  59)  and  VERWORN  ('89a,  pp.  8,  9). 
Fundamentally  similar  observations  have  been  made  by  KUHNE 
('64,  p.  79)  and  VERWORN  ('89b,  p.  274)  on  Myxomycetes, 
and  by  VERWORN  ('89%  pp.  13,  17)  on  the  rhizopods,  Poly- 
stomella  and  Pelomyxa.  So  these  data  may  be  considered  as 
of  general  worth  for  naked  protoplasm. 

Also  upon  ciliated  epithelium,  the  constant  current  acts 
as  a  very  strong  excitant,  producing  an  active  movement  in 
cilia  which  had  previously  nearly  ceased  to  beat.  This  excita- 
tion occurs,  especially  about  the  two  poles,  immediately  upon 
••  making  "  the  current.  (KRAFT,  '90,  pp.  234,  235.) 


130 


ELECTRICITY  AND  PROTOPLASM 


[Cn.  VI 


FIG.  28.  —  Actinosphserium  eichhornii  in  four  successive  stages  of  polar  excitation 
by  means  of  the  constant  electric  current.  Disintegration  begins  at  the  anode 
(+)  pole.  (From  VERWORN,  '95.) 

Allied,  apparently,  to  the  foregoing  phenomena  are  the  pro- 
toplasmic changes  which  follow  the  sudden  breaking  of  the 
current.  Unless  the  current  has  been  very  feeble,  the  pseudo- 
podia  of  Actinosphserium  begin,  at  the  moment  of  breaking,  to 
contract  and  become  varicose  upon  the  kathode  side,  while  the 
formerly  irritated  anode  side  is  quiet.  Thus,  the  breaking  of 
the  current  also  acts  as  a  stimulus,  but  this  is,  in  general, 
weaker  than  that  caused  by  making. 

If,  now,  a  current  which  endures  for  only  an  instant  —  if  a 
single  induction  shock  —  is  sent  through,  the  making  and  break- 
ing stimuli  are  practically  coincident,  and  a  violent  response 
may  be  called  forth.  Thus,  ENGELMANN  ('69,  p.  317)  found 
that  Amoeba,  subjected  to  a  strong  shock,  retracted  its  pseudo- 
podia,  and  assumed  a  spherical  form  within  two  seconds ;  and 
GOLUBEW  ('68,  p.  557)  has  described  a  similar  response  in 
leucocytes.  Under  similar  circumstances,  the  flagellum  of  the 
flagellate  Peranema  (Fig.  29)  made  an  energetic  stroke.  (VER- 
WORN, '95,  p.  414.)  I  have  spoken  above  as  though  there  were 
both  a  making  and  a  breaking  stimulus  ;  but  this  is  not  known 
to  be  the  case.  It  is  generally  recognized  from  experiments 


I 


EFFECT   ON  STRUCTURE   AND  FUNCTIONS 


131 


on  muscle,  that  it  is  the  "  making  "  only  of  a  single  induction 
shock  which  produces  the  response ;  but  VEKWORN  ('89%  pp. 
19-22)  has  found  that  in  the  rhizopod  Pelomyxa  it  is,  on  the 
contrary,  the  breaking  excitation  which  causes  the  response. 
The  subject  deserves  further  study. 

Finally,  the  effect  of  an  alternating  current  must  be  con- 
sidered. This  current  is  characterized  by  the  fact  that  it  is 
composed  of  a  series  of  rapidly  repeated  instantaneous  shocks 


spK&Vs* 

S^o^S^'^  ?.  ?. : 


FIG.  29.  —  Peranema.     a,  quietly  swimming;    b,  irritated  by  an  induction  stroke. 

(From  VERWORX,  '95.) 
FIG.  30.  —  Actinosphaerium  eichhornii,  STEIN.      Showing  effect  of  the  alternating 

current.    At  both  poles  the  pseudopodia  are  undergoing  a  disintegration,  which 

proceeds  equally  at  the  two  poles.     (From  VERWOBN,  '89.) 

which  alternately  reverse  their  direction.  Thus,  each  pole  of 
the  organism  subjected  to  such  a  current  receives  alternately 
the  making  (or  breaking)  effects  at  anode  and  kathode.  The 
maximum  action  is  thus  obtained.  When  an  Actinosphserium 
is  stimulated  by  such  a  current,  the  pseudopodia  at  both  poles 
contract  and  become  varicose ;  and,  finally,  the  protoplasmic 
substance  begins  to  disintegrate  and  to  flow  out  from  the  cell 
towards  the  two  electrodes,  until  the  body  acquires  a  biconcave 
form.  (VERWOKN,  '89%  p.  11.)  In  this  case  the  disintegra- 


OF   THF  "    "\ 

UNIVERSITY  ) 


132 


ELECTRICITY  AND  PROTOPLASM 


[Cn.  VI 


tion  takes  place  at  both  poles,  since  both  are,  alternately, 
anodes  (Fig.  30). 

Similar  effects  have  been  observed  in  other  cases.  Thus, 
when  an  amoeba  is  subjected  to  an  alternating  current,  it  be- 
comes spherical ;  the  protoplasmic  streaming  of  the  plasmodia 

of  a  myxomycete  ceases,  and, 
with  stronger  currents,  the 
whole  mass  contracts,  water 
being  forced  out.^  Finally, 
an  attempt  at  a  similar  re- 
sult is  seen  in  the  stamen- 
hair  cells  of  Tradescantia,  in 
which,  under  stimulation,  the 
protoplasmic  threads  segre- 
gate into  irregular  or  sphe- 
roidal clumps.  (KtiHNE,  '64, 
pp.  30,  31,  75,  99.)  In  all 
these  cases  we  see  that  the 
action  of  a  violent  current, 
like  repeated  contact,  leads 
(as  ENGELMANN,  '69,  p.  321, 
has  suggested)  to  results 
which  can  be  accounted  for 
on  the  ground  of  reduced 
cohesion,  —  first,  tendency  to 
spherical  aggregation,  and, 
finally,  disintegration  (Fig. 
31). 

After  having  studied  the 
effect  of  the  electric  current 
upon  Protista  and  simple 
cells,  it  remains  to  consider, 

very  briefly,  its  effect  upon  muscle  and  upon  nerve.  Since 
CALDANI  discovered,  in  1756,  that  frogs,  shortly  after  death, 
could  be  stimulated  to  movement  by  frictional  electricity,  and 
GALVANI  and  VOLTA,  towards  the  end  of  the  last  century, 
discovered,  by  the  same  response,  the  phenomenon  of  galvan- 
ism-, these  tissues  have  frequently  been  made  the  subject  of 
careful  experimentation.  It  has  been  shown,  not  merely  that 


FIG.  31.  —  One  of  the  cells  of  a  stamen  hair 
of  Tradescantia  virginica.  A,  unstimu- 
lated;  B,  stimulated  by  an  induction 
current.  At  a,  b,  c,  d,  the  protoplasm 
has  aggregated  into  drops  and  clumps. 
(From  VERWORN,  '89,  after  KUHNE, 
'64.) 


§2]  EFFECT   ON  STRUCTURE  AND  FUNCTIONS  138 

the  nerve  can  be  stimulated  to  its  functions,  but  that  muscle 
from  which  the  activity  of  the  nerve  has  been  excluded  by  the 
use  of  curare  (which  inhibits  the  action  of  the  nerve,  but  not 
of  the  muscle),  will  contract  upon  the  passage  of  a  current.) 

Upon  the  character  of  the  current,  however,  depends  that 
of  the  response ;  thus,  although,  as  we  have  seen,  a  closed 
constant  current  continues  to  stimulate  Protista,  it  has  been 
said  not  to  stimulate  nerve  or  muscle.  A  contraction  follows, 
it  has  been  maintained,  only  upon  considerable  variations  in  the 
electrical  condition,  such  as  result  from  making  or  breaking 
the  current.  It  is  probable,  however,  that  there  is  not  so  great 
a  difference  in  responsiveness  of  muscle  and  Protista  as  would 
seem  to  be  implied,  for  BIEDERMAXN  ('83)  has  shown  that  the 
constant  current  produces  a  whole  series  of  slight  contractions 
in  muscle  which  cannot  be  regarded  merely  as  a  secondary 
result  of  the  making  shock;  and  FICK  ('63)  has  observed 
contraction  due  to  the  constant  current  in  muscles  of  Lamel- 
libranchia.  So  that  even  in  muscles,  there  is  an  actual,  though 
weak,  response  to  a  steady,  constant  current,  j 

There  are  two  phenomena  following  momentary  shocks  ap- 
plied to  muscles  which  deserve  notice  in  passing.  First,  when 
a  single  induction  shock  is  passed  directly  through  a  muscle, 
we  notice  that  the  contraction  is  not  simultaneous  with  the 
shock,  but  follows  only  after  the  lapse  of  a  certain  ''latent 
period."  This  latent  period  represents,  it  is  believed,  time 
spent  in  transformations  going  on  in  the  plasma  preparatory  to 
contraction.  Secondly,  when  we  pass  (especially  in  a  muscle- 
nerve  preparation)  a  series  of  induction  shocks,  closely  following 
one  another,  as  in  the  alternating  current,  a  very  violent  con- 
traction is  produced,  since  the  new  shock  comes  to  the  muscle 
before  it  has  had  time  fully  to  relax,  and  causes  a  contraction  of 
the  already  contracted  tissue.  Thus  stimulus  is  superimposed 
upon  stimulus,  and  a  summated  response  (tetanus)  takes  place. 

» 

We  must  now  consider  more  carefully  a  subject  to  which 
we  have  hitherto  merely  alluded,  namely,  the  relation  to  the 
electrodes  of  the  point  of  the  organism  at  which  the  response 
first  appears.  Thus,  when  the  amoeboid  Pelomyxa  is  subjected 
to  the  constant  current,  a  contraction  appears,  at  the  time  of 


134 


ELECTRICITY  AND  PROTOPLASM 


[Cn.  VI 


making  the  current,  at  that  pole  only  which  is  turned  towards 
the  anode.  When  the  current  is  broken,  on  the  contrary,  a 
contraction  occurs  at  the  kathode,  the  pseudopodia  next  the 
anode  becoming  quiet.  (VERWORN,  '89a,  p.  19.)  This  relation 
may  be  expressed  in  tabular  form  as  follows  :  — 


AT  ANODE. 

AT  KATHODE. 

Upon  making  

excitation 

rest 

Upon  breaking  

rest 

excitation 

All  Protista  do  not,  however,  according  to  VERWORN,  respond 
in  the  same  way  as  Pelomyxa ;  thus,  with  the  constant  current 
of  a  certain  intensity,  he  got  in  both  Polystomella  crispa,  and 
Actinosphserium,  the  following  reaction  :  — 


AT  ANODE. 

AT  KATHODE. 

Upon  making 

excitation 

rest 

Upon  breaking  

rest 

rest 

It  must  be  said,  however,  that  the  reactions  obtained  in  any 
case  are  dependent  upon  the  strength  of  current  employed ; 
thus,  with  a  stronger  current,  the  following  result  was  obtained 
with  Actinosphyerium  :  — 


AT  ANODE. 

AT  KATHODE. 

Upon  making                      . 

excitation 

excitation 

Upon  breaking 

rest 

excitation 

A  comparison  of  the  last  two  tables  seems  to  indicate  that,  very 
probably,  with  a  current  intermediate  between  the  weak  and 
the  strong  current  employed,  we  should  get  a  result  like  that 
obtained  with  Pelomyxa.  At  any  rate,  we  may  say  that  all 
these  cases  tend  to  group  themselves  about  the  Pelomyxa  for- 
mula ;  —  making  :  anode,  excitation  ;  kathode,  rest ;  breaking  : 
anode,  rest ;  kathode,  excitation.  A  brief  designation  of  this 
type  is  desirable.  Since  the  condition  at  the  anode  upon 


§  2]  EFFECT  ON  STRUCTURE   AND   FUNCTIONS  135 

making  is  distinctive,  we  may,  call  this  the  anode-excitation 
tyr>e,  or,  briefer  still,  anex  type. 

C Turning,  now,  to  nerve  and  muscle  tissue,  we  meet  with  a 
type  of  response,  on  making  and  breaking  the  current,  alto- 
gether irreconcilable  with  this.  As  is  well  known,  when  a 
constant  current  is  made  or  broken,  all  the  tissue  lying  between 
the  electrodes  is  not  stimulated  at  one  time,  but  the  excitation 
makes  its  appearance  at  the  anode  or  kathode,  and  thence  is 
transmitted  to  the  other  pole.  One  can  demonstrate  this  on 
slow-moving  (e.g.  extremely  tired  or  dying)  muscle  at  the 
extremities  of  which  the  electrodes  are  placed.  The  contrac- 
tion begins  at  one  electrode,  and  travels  towards  the  other. 
By  using  more  refined  methods,  this  relation,  which  holds  for 
nerves,  striated  and  smooth  muscle  (cf .  ENGELMANN,  '70,  p.  302) 
has  been  formulated  as  follows  :  — 


AT  ANODE. 

AT  KATHODE. 

Upon  making  

T6St 

6xcit3/tion 

Upon  brGctkin0" 

sxcitcition 

l*6St 

This  is  seen  to  be  the  very  opposite  of  the  response  given  by 
Pelomyxa.  It  may  be  called  the  kathode-excitation  type,  or, 
in  brief,  the  katex  type. 

Having  now  seen  that  two  fundamentally  different  types  exist 
in  the  response  of  the  two  extreme  groups  of  the  animal  king- 
dom, the  question  arises,  what  is  the  distribution  of  these  types 
amongst  the  intermediate  forms  —  the  Invertebrate  Metazoa?  j 
Fortunately,  through  the  investigations  of  NAGEL  ('92  and  '92a), 
we  have  data  upon  this  subject.  In  NAGEL'S  experiments,  the 
whole  animal  was  employed,  the  two  electrodes  were  placed  at 
the  opposite  ends  of  its  long  axis,  the  metallic  circuit  was  then 
made  or  broken  as  required,  and  the  pole  (anode  or  kathode) 
at  which  contraction  first  occurred  was  noted.  Thus,  NAGEL 
found  that  when  the  current  was  made  through  the  sea-hare, 
Aplysia,  there  was  strong  excitation  and  momentary  retraction 
of  the  parts  next  to  the  ariode,  while  next  to  the  kathode  the 
body  showed  a  considerably  weaker  contraction.  Upon  break- 
ing the  current,  there  was  some  excitation  of  the  parts  of  the 


136 


ELECTRICITY  AND  PROTOPLASM 


[Cii.  VI 


body  next  to  the  kathode,  but  none  at  the  anode  end.  The 
result  that  one  obtains  depends,  ho\vever,  to  a  certain  extent, 
upon  the  strength  of  the  current  that  one  employs.  But  NAGEL 
did  not,  apparently,  measure  his  currents,  so  there  is  no  cer- 
tainty that  his  results  can  be  at  once  duplicated.  Taking  the 
results  for  various  Invertebrates  as  they  are  given,  however 
they  are  instructive. 

TABLE   XIII 


UPON  MAKING. 

UPON  BREAKING. 

AT  ANODE. 

AT  KATHODE. 

AT  ANODE. 

AT  KATHODE. 

LinmsBus                .  . 

excitation 

rest 

rest 

excitation 

Planorbis                   . 

excitation 

rest 

rest 

excitation 

Aplysia  punctata  .  . 

excitation  > 

excitation 

rest 

excitation 

Schseurgus  (octopod) 

excitation  > 

excitation 

rest 

excitation 

Helix  hortensis  .  .  . 

excitation  > 

excitation 

rest 

slight  excitation 

Ciona  intestinalis  .  . 

excitation  > 

excitation 

rest 

rest 

Janus  cristatus   .  .  . 

excitation  = 

excitation 

rest 

slight  excitation 

Pleurobranchia  .  .  . 

excitation  = 

excitation  * 

rest 

slight  excitation 

ISTassa  reticulata  .  .  . 

weak  excit. 

rest 

rest 

rest 

f  All  the  species  in  this  table  (all  of  which,  except  Ciona,  are 
Mollusca)  show  in  their  response  a  more  or  less  close  approach 
to  the  type  of  Pelomyxa  (excitation,  rest ;  rest,  excitation) ;  and 
we  may  believe  that  with  appropriate  stimulus  they  would  re- 
spond in  precisely  that  way. 

In  a  second  class  of  cases  the  response  of  the  whole  animal 
belongs  to  the  katex  type;  thus  two  species  examined  by 
NAGEL  showed  the  following  responses :  — 

TABLE   XIV 


UPON  MAKING. 

UPON  BREAKING. 

AT  ANODE. 

AT  KATHODE. 

AT  ANODE. 

AT  KATHODK. 

Pagurus  striatus    .  . 
Triton  cristatus  .  .  . 

rest 
excitation  < 

excitation 
excitation 

excitation 

rest 

*  Inconstant  in  occurrence. 


§2]  EFFECT   ON  STRUCTURE   AND  FUNCTIONS  137 

These  are  representatives  of  the  groups  Crustacea  and  Ver- 
tebrata. 

Among  all  the  species  studied  by  NAGEL  there  was  only  one 
which  gave  results  not  easily  assignable  to  either  of  the  two 
types.  This  organism  is  the  larva  of  a  dragon-fly,  JEschurea. 
Its  formula  is  excitation  =  excitation ;  rest,  rest.  NAGEL  says, 
however,  that  these  results  were  uncertain  and  variable. 

In  some  other  groups  studied  —  Ccelenterata  and  Echinoder- 
mata  —  the  current  used  provoked  no  response  at  either  pole ; 
while  with  Amphioxus  the  current  employed  produced  excita- 
tion at  both  poles  on  both  making  and  breaking  the  circuit. 
Such  variations  as  these,  are,  however,  easily  accounted  for  on 
the  ground  that  different  species  require  currents  of  different 
strengths  to  call  forth  what  may  be  termed  the  typical  response. 

Not  merely  between  different  groups  do  we  find  a  difference 
in  the  type  of  response,  but  even  inside  the  group  of  Protozoa 
dissimilarity  has  been  shown  to  occur.  Thus  VERWOKX  ('896, 
p.  301)  has  given  reasons  for  believing  that  three  flagellate 
species,  the  ciliate  Opalina,  and  some  bacteria  belong  to  the 
katex  type,  although  as  just  stated  (p.  133)  other  Protozoa 
exhibit  the  anex  type  of  response. 

Finally  it  appears  that  individuals  of  one  and  the  same  species 
subjected  to  different  intensities  of  current  may  give  rise  to 
responses  belonging  to  the  opposite  types.  Thus  when  a 
medium  current  is  "  made  "  through  Triton  cristatus  the  exci- 
tation is  greater  at  the  kathode  than  at  the  anode ;  but  when 
the  weakest  current  is  employed  a  making  response  occurs  at 
the  anode  only,  and  when  a  slightly  greater  intensity  is  used  the 
continuance  of  the  current  provokes  a  continuance  of  the  exci- 
tation at  the  anode.  (XAGEL,  '92%  p.  341.)  Likewise  the 
reaction  of  Vertebrate  muscle  varies  with  its  internal  condition. 
Thus  degenerated  or  over-stimulated  muscle  shows  predominat- 
ing anode  stimulation  on  making  the  current ;  and  transverse 
stimulation  of  the  muscle  fibre  gives  the  same  result.* 

(To  sum  up,  two  principal  types  of  response  to  the  electric 
current  may  be  distinguished :  the  first  or  anex  type  character- 
izing most  Protozoa,  Mollusca,  Vertebrates  (slightly  stimulated), 

*  For  a  discussion  of  these  cases  see  VERWOEN  ('89a,  p.  24). 


138  ELECTRICITY  AND   PROTOPLASM  [Cn.  VI 

and  weak  muscle  fibres ;  the  second  or  katex  type  found  espe- 
cially among  some  Flagellata,  Arthropoda,  and  Vertebrata.  A 
third  possible  type  (katanex  type)  is  certainly  of  very  limited 
distribution.  Between  the  two  types  we  notice  this  connecting 
link,  that  in  some  Vertebrates  a  weak  current  produces  one 
type  of  response ;  a  strong  current  the  other.  The  reason  for 
the  existence  of  these  two  distinct  types  —  one  of  which  char- 
acterizes animals  with  less  differentiated,  the  other  those  with 
more  differentiated,  muscular  and  nervous  systems  —  is  still 
greatly  in  need  of  investigation. 

The  nature  of  the  protoplasmic  change  wrought  by  the 
current  is  an  important  matter.  We  have  already  accounted 
for  the  effect  that  we  see  in  the  Protista,  on  the  ground  of  re- 
duced cohesion.  It  is  probable  also  that  the  current  gives  rise 
in  the  cytoplasm  to  chemical  changes  which  are  different  at  the 
two  poles.  It  is  well  known  that  when  a  current  is  passed 
through  a  neutral  solution  of  a  salt  there  is  produced  an  acid 
at  the  anode,  and  an  alkali  at  the  kathode.  Since  in  the  higher 
animals,  at  least,  the  body  contains  such  solutions,  it  seems 
probable  that  acid  and  alkaline  substances  are  here  likewise 
produced  by  the  passing  current.  This  probability  is  supported 
by  an  observation  of  KUHNE  ('64,  p.  100),  who  found  that  the 
violet  coloring  matter  of  the  stamen  hairs  of  Tradescantia 
v  become  changed  by  the  action  of  a  very  strong  induction  shock. 
He  says  that  a  change  in  the  violet  fluid,  like  that  which  occurs 
at  the  anode,  can  be  brought  about  by  dilute  hydrochloric  acid ; 
while  a  change  like  that  appearing  at  the  kathode  can  be  pro- 
duced by  potassic  hydrate.  An  observation  of  NAGEL  ('92a,  p. 
346)  suggests  also  that  the  current  acts  by  producing  a  chemi- 
cal change.  He  finds  that  that  part  of  the  body  of  the  snail 
and  the  leech  which  shows  most  markedly  the  anode-making 
excitation  is  coincident  with  that  which  is  most  sensitive  to 
chemical  substances.  So  that  the  reaction  to  a  galvanic,  still 
more  to  a  faradic,  stimulation  resembles  that  to  a  strong,  dis- 
agreeable taste  (quinine).  In  this  case  the  response  may 
result  either  from  the  chemical  substance  acting  directly  on 
the  muscles  or  attacking  first  the  sense  organs.  In  the  latter 
case  the  response  would  occur  through  the  mediation  of  the 
nervous  system? 


„ 


EFFECT  OX  STRUCTURE   AXD  FUXCTIOXS  139 


So  far  then  we  have  distinguished  two  chief  effects  of  the 
current  on  protoplasm  —  a  dissociation  effect  and  a  chemical 
effect.  It  may  now  be  worth  while  to  mention  that  there  is 
good  reason  for  believing  that  in  the  more  highly  differentiated 
animals,  like  Vertebrates,  not  all  protoplasm  is  affected  to  the 
same  degree  nor  in  the  same  way.  Thus  a  nervous  and  a 
muscular  effect  can  be  clearly  distinguished  in  frogs,  for  ex- 
ample. The  principal  effect  is  exerted  upon  the  central  nervous 
system,  for  HERMANN  ('86,  p.  415)  found  that  the  tail  of 
tadpoles  is  responsive  only  so  long  as  it  contains  a  piece  of 
spinal  nerve  ;  and  upon  frogs  subjected  to  curare,  which  inhib- 
its the  action  of  the  nerve  alone,  the  current  produces  a  much- 
diminished  effect,  giving  rise  merely  to  muscular  twitchingSo 
(BLASIUS  and  SCHWEIZER,  '93,  p.  528.)  Very  little  progress 
has  been  made,  however,  upon  the  determination  of  the  action 
of  different  intensities  upon  the  different  tissues  of  which  the 
Vertebrate  body  is  composed. 

We  have  seen  that  the  electric  current  provokes  a  response, 
and  we  have  seen  also  that  organisms  vary  in  their  responsive- 
ness so  that  a  current  strong  enough  to  call  forth  a  response  in 
one  species  is  not  sufficient  to  excite  another  species.  We  may 
say  that  the  one  species  is  attuned  to  a  different  strength  of 
current  from  the  other.  This  difference  in  responsiveness  indi- 
cates, of  course,  a  corresponding  difference  in  composition  of 
the  protoplasm.  Such  a  difference  may,  moreover,  be  produced 
in  a  single  individual  by  artificial  means.  These  means  are 
the  subjection  for  a  considerable  period  to  the  electric  current. 
Suppose  we  subject  an  organism  to  a  current  of  a  strength  only 
slightly  greater  than  that  just  necessary  to  provoke  a  response. 
After  the  current  has  acted  for  some  time  we  find  that  it  no 
longer  excites.  This  phenomenon  of  acclimatization  to  the 
galvanic  current  was  first  observed  among  the  Protista,  so  far 
as  I  know,  by  KUHXE  ('64,  pp.  76,  78),  who  found  that  in 
Mvxomycetes,  after  a  few  induction  shocks  had  been  sent 
through  the  plasmodium,  additional  shocks  of  the  same  intensity 
were  without  effect,  and  stronger  shocks  had  to  be  sent  through 
to  cause  contraction.  Similar  results  were  obtained  by  VER- 
X  ('89%  p.  10;  '89b,  p.  272)  in  subjecting  Actinosphserium 


140 


ELECTRICITY   AND   PROTOPLASM 


[CH.  VI 


and  Amoeba  to  a  weak  constant  current.  At  first  the  pseudo- 
podia  on  the  anode  side  plainly  retracted,  but  later  ceased  to 
do  so,  and,  finally,  the  current  still  passing,  the  retracted 
pseudopodia  began  to  extend  again.  The  action  of  the  current 
so  modified  the  protoplasm  as  to  change  the  attunernent  of  the 
organism. 

§  3.   ELECTROTAXIS 

In  studying  the  subject  of  aggregation  with  reference  to  the 
electric  current,  we  shall  consider  first  the  simplest  case  of  this 
phenomenon  as  it  is  exhibited  in  Amoeba ;  then  pass  to  the 
more  complex  forms  of  Protista,  especially  the  Ciliata,  and  after 


FIG.  32.  —  Galvanotaxis  of  Amoeba  diffluens.  A,  Amoeba  creeping,  unstimulated ; 
B,  after  closing  of  the  constant  current.  The  arrow  indicates  the  direction  of 
locomotion.  (From  VEBWOBN,  '95.) 

that  to  the  Metazoa.  After  dealing  with  the  phenomena  we 
must  attempt  to  explain  them. 

When  such  an  amoeba  as  that  shown  in  Fig.  32,  A,  is  sub- 
jected in  a  drop  of  water  to  the  action  of  a  weak  constant 
current,  as  already  indicated  (p.  129),  it  contracts,  especially 
upon  the  face  turned  towards  the  anode.  If  the  current  is  not 
strong  enough  to  produce  disintegration  at  that  pole,  but  only 
repeated  contraction,  and  if  meanwhile  the  kathode  pole  retains 
its  power  of  throwing  out  pseudopodia,  the  amoeba  must  grad- 
ually move  from  the  anode  (Fig.  32,  jB),  and  if  several  Amoebae 
are  under  the  cover-glass,  they  will  eventually  aggregate  about 
the  kathode.  Here  we  have,  then,  in  its  simplest  form,  a  case 
of  electrotaxis,  and,  since  the  organism  moves  toward  the 
negative  electrode,  we  may  call  it  negative  electrotaxis. 

If  now,  instead  of  an  amoeba,  we  watch  a  free  swimming 
flagellate  Infusorian,  —  Trachelomonas  hispida  (Fig.  33), — we 


§  3]  ELECTROTAXIS  141 

see  the  long-  flagellum  which  precedes  in  locomotion  coming  to 
lie  in  the  current  and  directed  towards  the  kathode,  so  that  the 
animal  migrates  in  that  direction.  The  following  explanation 
of  the  observed  fact  that  the  flagellum  becomes  directed  towards 
the  kathode  has  been  offered  by  VERWORN  ('89b,  p.  298).  ^The 
flagellum  and  the  pole  from  which  it  arises  constitute  the  most 
sensitive  end  of  the  body.  When  the  flagellum  is  stimulated 
it  beats  violently,  and  since  it  is  stimulated  most  when  turned 
towards  the  anode,  it  beats  most  violently  when  in  this  attitude. 
A  position  180°  from  this  is  one  of  comparative  rest.  In  interme- 
diate positions  the  degree  of  stimulation  is  intermediate.  After 
a  f CAV  strokes  the  body  will  "  naturally  "  come  to  assume  and  to 
retain  that  position  in  which  the  flagellum  is  least  stimulated. 
More  detailed  still  is  our  knowledge  of  electrotaxis  among 


FIG.  33.  —  Trachelomonas  hispida,  swimming  towards  the  kathode  (— )  upon  closure 
of  the  current.  The  arrow  shows  the  direction  of  locomotion.  (From  VER- 
WORX,  '89.) 

the  ciliate  Infusoria.  The  authors  who  have  worked  upon 
this  group  are  chiefly  VERWORX  ('89*  and  '89b)  and  LUDLOFF 
('95).  The  work  of  the  former  shows  that  the  phenomenon 
of  electrotaxis  is  exhibited  by  many  species,  especially  Para- 
mecium  aurelia  and  P.  bursaria,  Stentor  coerulens  and  S. 
polymorpha,  Pleuronema  chrysalis,  Opalina  ranarum,  Bursaria 
truncatella,  Halteria  grandinella  and  Stylonichia  mytilus. 
LUDLOFF  employed  only  Paramecium,  but  studied  it  much 
more  completely,  especially  using  various  currents  of  known 
relative  intensity.*  He  found  that  the  precision  with  which 

*  LUDLOFF  employed  a  trough  with  wax  walls,  clay  ends,  and  glass  bottom, 
and  used  brush  electrodes.  The  intensities  of  current  given  by  him  are  the 
readings  of  the  galvanometer.  The  cross-section  of  the  water  mass  in  which 
the  Paramecia  were,  and  over  which  the  current  spread  itself,  is  not  exactly 
given,  but  was  probably  about  20  sq.  mm.  If  we  employ  the  unit  of  strength 
recommended  by  HERMANN  and  MATTHIAS  (p.  128),  namely,  1  one-millionth  of 


142 


ELECTRICITY  AND   PROTOPLASM 


[Cn.  VI 


the  Paramecia  aggregated  at  one  pole  was  determined  by  the 
strength  of  the  current,  as  follows  :  A  current  of  3  8  caused 
in  general  a  movement  towards  the  kathode,  although  many 
individuals  appeared  not  to  be  affected  by  it.  In  20  seconds 
the  anode  end  of  the  fluid  was  almost  free  from  Infusoria. 
With  currents  of  6  $  and  15  8  the  aggregation  at  one  pole  be- 
came more  complete  and  took  place  in  a  short  time.  Indeed, 
there  was  a  relation  found  between  the  time  required  for 


f— 

^ 

o^uicon^oiOi-^i 
RELATIVE  RATES  OF  MIGRATION 

1 

\ 

/ 

\ 

/ 

\ 

/ 

f 

\ 

1 

v 

\ 

\ 

\ 

^* 

^ 

5 

^v. 

10(5       20(5       30d      40(5       50(5 

STRENGTHS  OF  CURRENTS 


60(5         70(5 


FIG.  34.  —  Curve  showing  relation  between  strength  of  currents  and  relative  time 
elapsing  before  Paramecia  have  aggregated  at  the  kathode.  The  ordinates  are 
measured  by  the  reciprocals  of  the  number  of  seconds  elapsing ;  the  abscissae,  by 
the  strength  of  current  in  5's. 

aggregation  at  the  kathode  and  the  strength  of  current 
employed,  which  is  instructive,  and  is  given  above  in  graphic 
form  (Fig.  34). 

This  curve  shows  that  as  the  current  increased  from  3  8  to 
21  8  the  rapidity  of  aggregation  increased,  but  as  the  current 
increased  still  further  this  rate  diminished  until  locomotion 
nearly  ceased  at  above  60  8.  The  intensity,  therefore,  of  21  8 
produced  the  most  rapid  movements. 

opening  the  current,  the  Infusoria  in  all  cases  swim, 


\  Upon 


1  ampere  per  sq.  mm.  (designated  5),  then  we  must  divide  LUDLOFF'S  galva- 
nometer readings  (given  in  milliamperes)  by  Tf£o»  or  (which  is  the  same  thing) 
multiply  them  by  50.  That  will  give  us  the  current  in  5's  per  sq.  mm.  All  of 
the  numerical  data  given  in  the  text  have  undergone  this  operation. 


B] 


ELECTROTAXIS 


143 


rapidly  for  a  moment,  towards  the  opposite  pole  (anode),  but 
then  quickly  begin  to  redistribute  themselves  throughout  the 
water.  This  redistribution  has  occurred  in  about  20  seconds 


FIG.  35.  —  Apparatus  for  studying  electrotaxis  of  Paramecium.  A  rectangular  trough, 
whose  ends  are  of  clay  and  sides  of  wax,  is  built  upon  a  glass  plate.  The  current 
is  applied  by  means  of  brush  electrodes.  The  direction  of  the  migration  of  the 
paramecia  is  indicated  by  the  arrow.  They  move  towards  the  kathode.  (From 
VERWORX,  '95.) 

after  the  current  is  broken,  and  the  time  is  independent  of  the 
strength  of  the  preexisting  current. 

The  movement  of  the  Infusorian  from  one  pole  to  the  other 
takes  place  along  the  lines  of  flow  of  the  current.  If  the  ter- 
minals are  two  parallel  plates,  these  lines  are  about  parallel 
(Fig.  35);  if  they  are  two  points  near  the  opposite  sides  of 


A  B 

FIG.  36.  —  Curves  made  by  Paramecia  in  its  galvanotactic  response  when  pointed 
electrodes  are  used  in  the  drop  of  water.  A,  beginning  of  migration  •  B,  com- 
plete aggregation.  (From  VERWORN,  '95.) 

a  water  drop,  the  lines  have  the  direction  of  the  lines  made 
by  iron  filings  scattered  on  a  plate  over  the  two  poles  of  a 
magnet  (Fig.  36). 

Besides  this  path  of  general  migration,  the  form  of  the  path 
followed  by  individuals  varies  with  the  current.  Normally 
Paramecium  moves  in  a  long  spiral.  As  the  current  is  in- 


144 


ELECTRICITY  AND  PROTOPLASM 


[Cn.  VI 


creased,  however,  this  spiral  becomes  shorter,  i.e.  has   more 
turns  per  centimeter  of  progression  from  one  pole  to  the  other 


\ 


FIG.  37.  —  Form  of  the  path  of  Paramecium  under  different  conditions,  a,  when  not 
subjected  to  the  constant  current  ;  &,  when  subjected  to  a  slight  current;  c,  when 
subjected  to  a  still  stronger  one.  (From  LUDLOFF,  '95.) 

(Fig.  37),  until  at  6.0  S,  in  making  one  turn  of  the  spiral,  the 
organism  progresses  hardly  more  than  its  own  length. 

Finally,  the  effect  of  the  current 
upon  the  movement  of  the  cilia  must 
be  considered.*  In  the  resting  Para- 
mecium the  cilia  rise  perpendicularly 
from  the  surface  of  the  body  (Fig.  38). 
If  an  individual  stands  with  its  ante- 
rior (blunt)  end  towards  the  anode, 
and  a  current  of  8  8  passes  through, 
the  cilia  at  the  posterior  (kathode) 
end  begin  to  vibrate.  If  the  individ- 
ual lies  transverse  to  the  current  and 
the  current  is  closed,  the  cilia  on  the 
kathode  side  vibrate,  those  on  the 

a   cur_ 


FIG.  38.  -Paramecium,  show-     anode  gide  being. 
ing  position  of  cilia  when  .    . 

unstimuiated.    The  blunt    rent  of  16  o  one  can  see  that  the  kath- 

end  is  anterior.     (From    ode  stimulation  increases  the  forward 

(anteriad)  phase  of  the  cilium  move- 

ment (the  "recovery").     With  an  intensity  of  24  8,  vibration 
of  cilia  occurs  at  both  kathode  and  anode.     It  is,  however,  more 

*  LUDLOFF  was  enabled  to  make  a  careful  study  of  the  effect  of  the  current 
on  the  cilia  by  making  use  of  gelatine  solutions  such  as  have  been  recommended 
by  JENSEN  ('93,  p.  556). 


. 


3]  ELECTROTAXIS  145 


intense  at  the  kathode  and  is  also  in  opposite  directions  at  the 
two  poles.  This  law  is  important,  and  may  be  thus  formulated: 
The  current  intensifies  at  the  anode  the  backward  movements  and 
at  the  kathode  thefonvard  movements  of  the  cilia,  and  the  latter 
are  more  intensified  than  the  former ;  or,  in  other  words,  the 
anode  stimulation  increases  the  effectiveness  of  the  normal 
stroke,  the  kathode  stimulation  diminishes  the  effectiveness  of 
the  normal  stroke,  and  the  diminishing  effect  is  the  greater  of 
the  two. 

On  the  basis  of  these  observed  facts,  LTJDLOFF  has  proposed 
a  theory  which  accounts  for  several  of  the  electrotactic  phe- 
nomena in  the  Ciliata,  especially  the  fact  that  with  strong 
currents  there  is  a  diminution  in  the  rate  of  locomotion,  and 
that  at  a  lower  intensity  the  axis  of  the  organism  is  placed  in 
the  axis  of  the  current,  with  its  anterior  end  towards  the 
kathode.  This  theory  may  be  stated  as  follows:  In  every  com- 
plete swing  of  a  cilium  two  phases  may  be  distinguished  — 
the  backward  "stroke"  and  the  forward  "recovery."  Nor- 
mally the  stroke  is  the  more  effective,  otherwise  forward  loco- 
motion would  not  occur."N>  The  excess  in  effectiveness  of  the 
stroke  may  be  designated  by  the  quantity  x.  Let  us  assume  a 
Paramecium  lying  in  the  axis  of  the  current  with  its  anterior 
end  towards  the  kathode.  Then  the  stimulus  received  at  the 
anode  or  hinder  end  increases  the  effectiveness  of  the  stroke  by 
a  quantity  which  we  may  designate  m.  Thus  the  excess 
energy  of  the  stroke  over  recovery  is  for  these  hinder  cilia 
x  +  m.  The  stimulus  received  at  the  kathode  or  anterior  end 
diminishes  the  effectiveness  of  the  stroke  by  a  quantity  which 
we  may  call  n,  which  is  larger  than  m.  Here  the  excess  energy 
of  stroke  over  recovery  is  x  —  n.  If  at  any  intensity  of  cur- 
rent n  exceeds  x,  the  anterior  cilia  will  work  to  oppose  the 
forward  motion  of  the  individual,  and  when  n  —  x  =  x  +  m  loco- 
motion will  not  occur.  Such  a  strength  of  current  probably 
occurred  in  the  experiment  given  on  p.  142,  where  locomotion 
ceased  at  above  60  B. 

To  account  for  orientation  of  the  axis  and  its  anterior 
end,  we  have  merely  to  apply  the  general  law  given  above. 
Let  us  suppose  that  we  are  observing  a  Paramecium  lying  in 
the  axis  of  a  current  of  medium  intensity,  with  its  anterior 


146 


ELECTRICITY  AND  PROTOPLASM 


[CH.  VI 


end  towards  the  anode.  Since  n  is  here  supposed  to  be  less 
than  x,  the  resultant  effect  is  to  move  the  animal  forward.  In 
moving  forward  in  its  spiral  course,  one  side  becomes  presented 
to  the  anode.  On  this  side  the  excess  of  energy  of  the  stroke 
is  x  +  m,  while  on  the  kathode  side  it  is  x  —  n.  The  resultant 
effect  of  the  cilia  on  the  two  sides  forms  a  couple  which  revolves 
the  organism  about  one  of  its  short  axes  until  it  comes  again 
into  the  axis  of  the  current,  but  with  its  anterior  end  towards 
the  kathode.  The  beating  of  its  cilia  must  now  carry  it  towards 
the  kathode  (Fig.  39). 


FIG.  39.  —  Diagram  showing  the  successive  attitudes  (a,  6,  c,  d,  and  e)  assumed  by 
Paramecium  when  its  head  is  turned  towards  the  anode  at  the  beginning  (a).  It 
rotates  till  its  head  is  next  the  kathode  (e) .  (From  LUDLOFF,  '95.) 

Before  leaving  the  Protozoa,  we  ought  to  look  over  the  whole 
field.  We  have  hitherto  considered  only  cases  of  migration 
towards  the  kathode  —  negative  galvanotaxis.  VERWORN 
('89b),  however,  has  found  that  some  Protista  are  positively 
electrotactic ;  namely,  the  flagellata,  Polytoma  uvella,  Crypto- 
monas  ovata,  and  Chilomonas  paramecium;  the  ciliate,  Opalina; 
and  some  bacteria.  Finally,  VERWORN  ('95,  p.  446)  describes 
one  of  the  elongated  Ciliata  —  Spirostomum  ambiguum — which 
places  its  long  axis  across  that  of  the  current  and  migrates 
towards  neither  pole,  a  condition  which  may  be  called  (after 
VERWORN)  transverse  electrotaxis. 

Passing  now  to  the  Metazoa,  we  find  investigations  concern- 
ing electrotaxis  among  Invertebrates  by  NAGEL  ('92  and  '92a 


~,q 


ELECTROTAXIS 


147 


v  t 

$ 


and  '95),  and   BLASIUS  and  SCHWEIZER  ('93) ;    and   among 
Vertebrates  by  these  authors  and  also  HERMANN  ('85  and  '86), 

AVALD  ('94,  '94%  and  '94b),  HERMANN  and  MATTHIAS  ('94),  and 
ALLER  ('95).  The  number  of  species  investigated  has  been 
considerable.  I  give  below  a  table  of  the  Invertebrate  genera 
studied  and  the  sense  (-f  t>r  — )  of  their  response  at  the  given 
intensity  of  currents.  Barely  rough  quantitative  expression 
of  strength  of  current  can  be  deduced  from  NAGEL'S  paper. 
Where  no  data  are  given  the  currents  are  supposed  to  be  of 
intermediate  strength.  N.  stands  for  NAGEL,  B.S.  for  BLA- 
SIUS and  SCHWEIZER.  The  numbers  which  follow  give  the 
year  of  publication  and  the  page. 


TABLE   XV 


SPECIFIC  NAME. 

STRENGTH  OF 
CURRENT. 

SENSE  OF 
RESPONSE. 

AUTHORITY. 

Mollusca  : 
Limn86a  stagnalis  

weak 

N.  '95 

Var.  other  Gastropoda  (probably)  . 

Annelida  : 
Lunibricus 

— 

N.  '92»;  '95 
N  '95  6°6 

Tubifex  rivuloriim                          . 

N  '95  631 

Hirudo  medicinalis  

0.88 

B.S.  '92,  516 

Branchiobdella  parasitica  

B.S.  '92,  516 

Crustacea  : 
Cyclops  

strong 

-}. 

N.  '92,  629 

Asejlus  aouaticus  •           

strong 

4- 

N.  '95  633 

Astacus  fluviatilus 

048 

_i_ 

B  S.  '92  518 

In  sect  a  : 

-f  ? 

N.  '95,  636 

-f 

N.  '95,  636 

Dytiscus  marginalis  

1.98 

+ 

B.S.  '92,  519 

Hydrophilus  piceus  

198 

B.S.  '92,  519 

From  this  table  it  appears  that  Mollusca  and  Annelida  are 
usually  negatively  electrotactic  to  a  current  of  medium  inten- 
sity, while  Arthropoda  are  mostly  positively  electrotactic  to 
such  a  current.  It  is  noteworthy,  however,  that  two  quite 


148  ELECTRICITY  AND  PROTOPLASM  [Cn.  YI 

closely  allied  beetles  like  Dytiscus  and  Hydrophilus  should 
by  the  same  observers  be  found  to  react  in  different  ways. 

In  addition  to  the  species  named,  some  have  been  studied 
which  have  given  no  results.  Thus  NAGEL  ('95,  p.  639)  ob- 
tained no  response  from  the  larva  of  Libellula  depressa,  even 
with  a  wide  range  of  current-intensities. 

Passing  now  to  the  Vertebrata,  we  enter  a  region  in  which, 
as  a  result  of  more  numerous  studies,  the  data  are  more  volu- 
minous, but  at  the  same  time  less  in  accord.  Since  many  mat- 
ters are  here  still  in  dispute,  we  may  best  consider  historically, 
i.e.  in  chronological  sequence,  what  has  hitherto  been  done  in 
this  field. 

vThe  first  person  to  describe  the  phenomenon  of  electrotaxis 
in  Vertebrates  —  as,  indeed,  in  any  organism  —  was  HERMANN 
('85,  '86).  j  He  used  frog  larvae  14  days  old,  held  in  a  shallow 
rectangular  porcelain  trough,  along  the  two  small  sides  of  which 
thick  zinc  wires  were  placed,  connected  with  a  chain  of  20  small 
zinc-carbon  elements.  No  mention  of  the  strength  of  the  cur- 
rent except  such  as  can  be  gained  from  these  facts  was  made. 
This  omission  of  quantitative  details  is  to  be  regretted,  since 
had  the  strength  of  current  to  which  the  organisms  were  sub- 
jected been  given,  much  subsequent  confusion  might  have  been 
avoided.  With  this  current,  then,  of  unknown  intensity,  flow- 
ing through  the  water  containing  the  larvae,  all  of  the  latter 
were  seen  to  place  themselves  in  the  axis  of  the  current  with 
their  heads  directed  toward  the  anode.  This  orientation  was 
the  consequence  of  the  fact  that  a  current  passing  cephalad 
through  the  larva  acted  as  a  violent  stimulus ;  but  while 
passing  caudad  it  brought  stupefaction  or  even  (temporary) 
paralysis. 

The  results  obtained  by  HERMANN  were  now  confirmed  and 
extended  by  BLASIUS  and  SCHWEIZER  ('93).  They  employed 
a  wooden  trough  with  sheet  zinc  electrodes  of  nearly  the  cross- 
section  of  the  smaller  ends  of  the  trough,  and  experimented 
upon  fishes,  Salamandra,  and  the  frog.  The  weakest  current 
employed  was  0.35  B  to  0.47  8,  which  merely  affected  the  char- 
acter of  the  swimming  of  the  fish  subjected  to  it,  without 
determining  its  direction.  The  next  stronger  current  men- 
tioned was  1.58S.  With  this  current  a  marked  orientation  of 


I 


3]  ELECTROTAXTS  149 


the  fish  with  their  heads  to  the  anode  was  noticed.  With 
Salamandra  larvae  currents  of  2.38  to  4.78  were  chiefly  em- 
loyed.  In  the  experiments  of  BLASIUS  and  SCHWEIZER  the 
organisms  sometimes  migrated  toward  the  anode,  if  the  cur- 
rent was  not  so  strong  as  to  stupefy,  but  they  lay  stress  upon 
the  point  that  the  migration  is  a  secondary  phenomenon  —  that 
the  orientation  is  the  primary  effect  of  the  current. 

Xext  came  the  observations  of  EWALD  ('94),  who  used  very 
young  tadpoles  (5  days)  and  non-polarizable  points  as  elec- 
trodes. Thus  he  was  not  able  to  give  the  strength  of  current 
to  which  the  individuals  were  subjected.  His  results  seemed 
directly  to  oppose  those  of  the  two  preceding  authors,  for 
with  his  (unknown)  current,  the  tadpoles  were  stimulated 
when  the  current  passed  caudad  and  stupefied  by  one  passing 
cephalad ;  also  they  placed  themselves  in  the  axis  of  the  cur- 
rent with  their  heads  towards  the  kathode.  The  larvae  did 
not  seem  to  find  this  position  as  a  direct  response  to  stimulus, 
but  whenever  an  individual,  in  its  turnings  to  the  right  and 
left,  fell  into  this  —  electrotactic  —  position  it  was  no  longer 
stimulated,  but  stupefied,  and  so  came  to  rest. 

These  discordant  results  of  EWALD  led  HERMANN,  with  his 
student  MATTHIAS,  again  into  the  discussion.  By  careful 
measurements  of  the  strength  of  current,  they  found  that 
between  0.38  and  1.5  &  frog  tadpoles  of  from  1  to  3  weeks  old 
did  face  the  kathode,  as  EWALD  fojund,  and  did  move  towards 
it.  But  HERMANN  and  MATTHIAS  ('94)  believed  this  result 
to  be  due  to  the  fact  that  only  cephalad-flowing  currents  of  this 
intensity  excite,  and  thus  only  such  currents  are  able  to  pro- 
duce locomotion. 

EWALD  ('94b),  however,  cannot  accept  their  idea  that  a 
caudad-passing  current  of  small  intensity  produces  no  excita- 
tion, for,  he  says,  he  has  seen  small  fish,  lying  with  face  to  the 
anode,  made  to  move  towards  the  kathode  by  the  action  of  the 
weak  current.  Since  HERMANN  and  others  have  shown  that 
very  strong  currents  cause  paralysis  even  when  flowing  cepha- 
lad, EWALD  concludes  that  we  must  recognize  the  existence  of 
three  different  effects  at  three  intensities;  weakest,  medium, 
and  strongest.  The  medium  current  (which  has  the  broadest 
range)  is  that  by  which  the  organisms  are  irritated  as  it  flows 


150  ELECTRICITY  AND  PROTOPLASM  [Cn.  VI 

cephalad,  so  that  they  come  to  lie  with  head  towards  anode ; 
the  weakest  current  is  that  by  which  (following  EWALD) 
the  organisms  are  irritated  as  it  flows  caudad,  so  that  they 
come  to  lie  facing  the  kathode ;  finally,  the  strongest  cur- 
rent is  that  at  which  a  violent  stimulation  leading  to  paraly- 
sis is  produced  by  the  cephalad-flowing  current  (as  well  as 
the  caudad?). 

•  In  seeking  for  an  explanation  of  electrotaxis  in  Metazoa,  it  is 
necessary,  first  of  all,  to  notice  that  there  is  a  close  relation 
between  response  to  the  make-shock  (as  described  on  pp.  136, 
137)  and  the  direction  of  orientation  of  the  body  in  electro- 
taxis.  Thus  all  gastropods  studied  are,  upon  making,  excited 
chiefly  at  the  anode,  and,  correspondingly,  all  gastropods  hitherto 
studied  when  subjected  to  the  current  face  the  kathode  ;  so  on 
the  other  hand,  such  Crustacea  as  have  been  studied  are  stimu- 
lated at  the  kathode,  and  they  accordingly  come  to  face  the 
anode.  In  regard  to  Vertebrates,  we  have  apparently  a  double 
electrotactic  orientation  varying  with  the  current,  and  corre- 
spondingly we  have,  as  NAGEL  has  shown  (p.  137),  a  double 
irritability  depending  on  the  current.  A  medium  current  pro- 
duces a  kathode  excitation  and  an  anode  orientation ;  while 
the  weakest  current  produces  an  anode  excitation  and  a 
kathode  orientation.  So  we  may  lay  it  down  as  a  general 
law :  Positively  electrotactic  organisms  exhibit  the  katex  type  of 
irritability;  and  negatively  *  electrotactic  organisms  exhibit  the 
anex  type  or,  in  general,  the  electrotactic  organism  turns  tail  to 
the  exciting  pole. 

EWALD  ('94,  pp.  611-615)  accounts  for  this  difference  of 
response  of  Vertebrates  to  weak  and  strong  currents,  by  the 
aid  of  certain  observations  that  he  made  upon  the  excitation 
of  the  nerve  cord.  We  have  already  seen  that  the  making 
of  the  medium  constant  current  stimulates  at  the  kathode,  so 
that  an  animal  turns  tail  to  the  kathode.  EWALD  found  that 
the  two  parts  of  the  dorsal  nerve  were  differently  stimulated 
by  the  current ;  the  brain  was  stimulated  chiefly  by  a  caudad- 
passing  current ;  the  spinal  cord  chiefly  by  a  cephalad-passing 
current.  This  conclusion  was  established  by  two  experiments. 
First,  the  two  electrodes,  placed  a  few  millimeters  apart,  are 
brought  into  contact  with  different  parts  of  the  body  of  a  fish. 


SUMMARY  OF   THE   CHAPTER  151 


Let  the  current  be  passing  through  the  fish  from  the  anterior  to 
the  posterior  electrode.  At  the  tail  end  we  get  no  excitation  ; 
and,  as  we  pass  forward,  the  body  remains  quiet  until,  pass- 
'ing  the  region  of  the  medulla  oblongata,  an  excitation  appears. 
If  the  operation  is  repeated  with  a  reverse  current,  we  get 
excitation  behind  the  head  and  quiet  on  the  head.  Secondly, 
if  a  frog  larva  be  cut  in  two  transversely  at  the  root  of  the 
tail,  the  head  end  is  irritated  only  by  a  caudad-flowing  cur- 
rent ;  the  tail  end  only  by  a  cephalad-flowing  current ;  while 
in  both  cases  the  opposite  current  quiets.  (Cf.  also  EWALD, 
'94b,  p.  162.)  These  observations  were  now  made  use  of  to 
explain  the  opposite  orientation  of  the  tadpole  in  the  presence 
of  weak  and  strong  currents.  NAGEL  assumed  that  the  weak- 
est currents  can  affect  the  brain  only.  Now  if  that  current 
runs  caudad,  it  will  strongly  stimulate  the  body  so  that  it  turns 
tail  to  the  anode.  The  medium  currents,  however,  stimulate 
the  whole  dorsal  nerve,  but  the  spinal  cord  to  a  preponderating 
degree,  so  that  a  cephalad-passing  current  irritates  more  than  a 
caudad  current,  and  the  animal  will  turn  tail  to  the  kathode. 
Thus  weaker  or  stronger  current  will  determine  —  or  4- 
electrotaxis. 

SUMMARY  OF  THE  CHAPTER 

Electricity  affects  protoplasm  in  two  principal  ways  :  first,, 
by  causing  contraction  ;  second,  by  determining  orientation. 
We  can  distinguish  two  principal  types  of  contraction  phe- 
nomena and,  corresponding  to  and  dependent  upon  these,  two 
types  of  orientation  phenomena.  The  first  type  of  contraction 
is  that  which  is  produced,  upon  making  the  constant  current, 
chiefly  at  the  anode  ;  the  second  is  produced  chiefly  at  the 
kathode.  The  corresponding  orientation  or  migration  types 
are,  facing  the  kathode  and  facing  the  anode.  Since  the  orien- 
tation phenomena  are  dependent  upon  the  contraction  phe- 
nomena, the  most  important  causes  to  be  investigated  are,  first, 
that  of  contraction,  and  second,  that  of  the  difference  in  type 
of  contraction  exhibited  by  different  organisms.  The  funda- 
mental teaching  of  this  chapter  is  that  the  electric  current  acts 
as  a  stimulus  upon  protoplasm,  and  may  determine  the  charac- 
ter of  its  activities. 


152  ELECTRICITY  AND   PROTOPLASM  [Cn.  VI 


LITERATURE 

BIEDERMANN,  W.  '83.     Ueber  rythmische  Contraction  quergestreifter  Mus- 

keln  unter  dem  Einflusse  des  constanten  Stromes.    Sitzb.  Wien.  Akad., 

Math.-Nat.  Cl.     LXXXVII,  Abth.  3,  pp.  115-136.     Taf.  I-II,  1883. 
BLASIUS,  E.  and   SCHWEIZER,  F.  '93.      Electrotropismus   und  verwandte 

Erscheinungen.     Arch.  f.  d.  ges.  Physiol.      LIII,  493-543.     10  Feb. 

1893. 
ENGELMANN,  T.  W.  '69.     Beitrage  zur  Physiologic  des  Protoplasma.     Arch. 

f.  d.  ges.  Physiol.     II,  307-322. 
70.     Beitrage  zur  allgemeinen  Muskel-  und  Nervenphysiologie.     Arch,  f . 

d.  ges.  Physiol.     Ill,  247-326. 
EWALD,  J.  R.  '94.     Ueber  die  Wirkung  des  galvanischen  Stroms  bei  der 

Langsdurchstromung  ganzer  Wirbelthiere.     Arch.  f.  d.  ges.  Physiol. 

LV,  606-621.     10  Feb.  1894. 

'94a.     Berichtigung.     Arch.  f.  d.  ges.  Physiol.     LVI,  354.     11  Apr.  1894. 
'94b.    Ueber  die  Wirkung  des  galvanischen  Stroms  bei  der  Langsdurch- 
stromung ganzer  Wirbelthiere.      II   Mitth.  Arch.  f.  d.  ges.  Physiol. 

LIX,  153-164.    30  Nov.  1894. 
•FiCK,  A.  '63.     Beitrage  zur  vergleichenden  Physiologic  der  irritablen  Sub- 

stanzen.     Braunschweig.     1863.     (Not  seen.) 
GOLUBEW,  A.  '68.     Ueber  die  Erscheinungen,  welche  elektrische  Schlage 

an  den  sogenannten  farblosen  Formbestandtheilen  des  Blutes  hervor- 

bringen.    Sitzb.  Wien.  Akad.,  Math.-Nat.  Cl.    LVII,  Abth.  2,  555-572. 
HERMANN,  L.  '85.     Eine  Wirkung  galvanischer  Strome  auf  Organismen. 

Arch.  f.  d.  ges.  Physiol.     XXXVII,  457-460.     2  Dec.  1885. 
'86.     Weitere  Untersuchungen  iiber  das  Verhalten  der  Frochlarven  im 

galvanischen  Strome.      Arch.  f.  d.  ges.  Physiol.      XXXIX,  414-419. 

21  Oct.  1886. 
HERMANN,  L.  and  MATTHIAS,  F.  '94.     Der  Galvanotropismus  der  Larven 

von  Rana  temporaria  und  der  Fische.    Arch.  f.  d.  ges.  Physiol.    LVII, 

391-405.     20  July,  1894. 
JENSEN,  P.  '93.     Methode  der  Beobachtung  und  Vivisektion  von  Infusorien 

in  Gelatinelosung.     Biol.  Centralbl.     XII,  556-560.     1  Oct.  1892. 
KRAFT,  H.  '90.     Zur  Physiologie  des  Flimmerepithels  bei  Wirbelthieren. 

Arch.  f.  d.  ges.  Physiol.     XL VII,  196-235.     9  May,  1890. 
KUHNE,  W.  '64.      Untersuchungen   iiber  das   Protoplasma  und   die   Con- 

tractilitat.     Leipzig:  Engelmann.     1864. 
LUDLOFF,  K.  '95.     Untersuchungen  iiber  den  Galvanotropismus.     Arch.  f. 

d.  ges.  Physiol.     LIX,  525-554.     5  Feb.  1895. 
NAGEL,  W.  A.  '92.     Beobachtungen  iiber  das  Verhalten  einiger  wirbelloser 

Thiere  gegen  galvanische  und  faradische  Reizung.     Arch.  f.  d.  ges. 

Physiol.     LI,  624-631.     26  March,  1892. 
'92a.     Fortgesetzte  Beobachtungen  iiber  polare  galvanische  Reizung  bei 

Wasserthieren.     Arch.  f.  d.  ges.  Physiol.      LIII,  332-347.      24  Nov. 

1892. 


LITERATURE  153 

XAGEL,  W.  A. '95.    Ueber  Galvanotaxis.    Arch,  f .  d.  ges.  Physiol.    LIX,  603- 

642.     5  Feb.  1895. 
OSTWALD,  W.  '94.    Manual  of  Physico-chemical  Measurements.    Translated 

by  J.  Walker.     255  pp.     London :  Macmillan.     1894. 
VERWORX,  M.  '89*.     Die  polare  Erregung  der  Protisten  durch  den  galva- 

nischen  Strom.     Arch.  f.  d.  ges.  Physiol.     XLV,  pp.  1-36.     23  March, 

1889. 
'89b.     The  same  (continued).     Arch.  f.  d.  ges.  Physiol.     XL VI,  pp.  267- 

303.     18  Xov.  1889. 
'95.     (See  Chapter  IV.) 
WALLER,  A.  D.  '95.     Galvanotropism  of  Tadpoles.     Science  Progress.    IV, 

96-103.     Oct.  1895. 


CHAPTER  VII 
ACTION  OF  LIGHT   UPON  PROTOPLASM 

IN  this  chapter  it  is  proposed  to  discuss  (I)  the  application 
and  measurement  of  light ;  (II)  its  chemical  action ;  (III)  the 
effect  of  light  upon  the  general  functions  of  organisms;  and' 
(IV)  the  control  of  locomotion  by  light  —  phototaxis  and 
photopathy. 

§  1.   THE  APPLICATION  AND  MEASUREMENT  OF  LIGHT 

Light,  which  as  a  form  of  radiant  energy  is  closely  related  to 
radiant  heat,  is  always  accompanied  by  a  certain  quantity  of 
heat,  whose  action  (in  at  least  one  control  experiment  in  every 
set)  should  be  eliminated.  To  cut  out  heat  without  great  loss 
of  light,  we  must  employ  transparent  adiathermal  media.  Of 
these,  a  plate  of  ice  is  the  most  effective,  but  alum,  on  account 
of  its  higher  melting  point,  is  more  convenient.  A  parallel- 
sided  vessel  full  of  distilled  water,  or,  still  better,  a  saturated 
aqueous  solution  of  alum,  forms  an  inexpensive,  highly  adi- 
athermal screen. 

The  quality  of  the  light  used  in  any  experiment  should  be 
carefully  determined.  If  any  other  light  than  that  of  the  sun 
or  incandescent  solids  is  employed,  it  should  be  subjected  to 
spectroscopic  analysis.  For  biological  purposes  a  direct-vision 
hand  spectroscope,  such  as  BROWNING'S,  is  convenient  and 
adequate. 

Often  monochromatic  light  or  a  definite  range  of  the  spectrum 
is  desired.  This  may  be  obtained  in  various  ways.  The 
purest  monochromatic  light  can  be  got  by  making  a  long  spec- 
trum and  using  the  desired  part  of  it.  To  make  such  a  spec- 
trum one  may  employ,  in  a  dark  room,  a  lamp,  followed  in 
succession  by  a  slit  and  a  lens  to  form  an  image  of  the  slit 

154 


§  1]         APPLICATION  AND  MEASUREMENT  OF  LIGHT         155 

on  a  prism  of  bisulphide  of  carbon,*  which  gives  very  great 
dispersion  of  the  rays. 

In  defining  the  regions  of  the  solar  spectrum  which  are 
employed  in  any  study,  it  is  usual  to  make  reference  to  the 
dark  absorption  bands  (FRAUEXHOFER'S  lines)  which  cross 
the  solar  spectrum.  The  largest  of  these  are  lettered,  begin- 
ning with  A  in  the  visible  red  and  ending  with  H  in  the 
visible  violet.  At  other  times  it  may  be  more  convenient  to 
define  any  part  of  the  spectrum  by  means  of  the  extreme 
wave  lengths  between  which  it  lies.  Lithographs  showing  the 
spectral  colors  and  the  wave  lengths  corresponding  thereto 
are  given  in  encyclopaedias  and  most  of  the  text-books  on 
physics.  A  crude  attempt  is  made  to  show  the  relation  be- 
tween color  and  wave  length  in  Fig.  40.  The  wave  lengths  at 


Red    Orange      Yellow      Green        Blue 


Indigo 


Violet 


1 

! 

1 

\ 

V  1701 

65 

CO 

1 
1 

5 

5 

i 

! 

5 

0 

\ 

i 

5 

4 

1    | 

! 

j 

i 

!   J 

i 

! 

! 

aBC  Eb          F  G  h 

FIG.  40.  —  Diagram  of  the  solar  spectrum  showing  the  main  absorption  bands  and  the 
range  of  the  various  spectral  colors.  The  numbers  are  wave  lengths  in  hundred- 
thousandths  of  a  millimeter.  (From  REIXKE,  '84.) 

the  different  absorption  bands  are  given  more  exactly  (in  thou- 
sandths of  a  millimeter,  =  /i)  •  in  the  following  table,  and  also 
the  number  of  waves  per  second  in  1012ths. 


TABLE   XVI 


ABSORPTION 
BAKD. 

WAVE  LENGTH, 
A. 

VIBRATION'S  PEK 
SECOND  n  x  1012. 

ABSORPTION 
BAND. 

WAVE  LENGTH, 
A. 

VIBRATIONS  PER 
SECOND  n  x  10". 

A  

0.760  /A 

392 

E 

0.527  p 

566 

B  

0.687  fj. 

433 

F 

0.486  fj. 

613 

C  

0.656  p. 

454 

G 

0.431  IJL 

692 

D  

0.589  fj. 

506 

H.  .  .  . 

0.397  /x 

751 

*  The  bisulphide  prism  may  be  made  as  follows :  Upon  a  thick  glass  plate 
three  rectangular  pieces  of  glass  of  equal  size  are  placed  perpendicularly,  so  as 


156  LIGHT   AND  PROTOPLASM  [On.  VII 

Extreme  ultra-violet  X  =  0.295/*;    1010  x  1012  vibrations  per 
second. 

To  obtain  monochromatic  light  from  the  spectrum,  REINKE'S  ('84)  spec- 
trophor  will  be  found  useful  (Fig.  41).  In  this  instrument  a  beam  of  sun- 
light cast  by  a  heliostat  through  a  slit  at  H  is  converged  by  means  of  an 
interpolated  lens,  0,  upon  a  prism,  P,  set  at  the  angle  of  minimum  devia- 
tion. Passing  through  this  prism  the  rays  are  dispersed  and  a  spectrum  is 
formed  upon  a  diaphragm  D,  Dl  composed  of  halves  bounding  a  second  slit 
whose  position  and  width  may  be  varied  at  will  so  as  to  include  any  desired 
part  of  the  spectrum.  A  large  lens  C  known  as  the  collector  brings  the 
rays  which  have  passed  through  the  second  slit  to  a  focus  at  E.  Just  in 


FIG.  41.—  Diagram  showing  the 
construction  of  REINKE'S 
spectrophor  and  the  path 
of  the  rays  in  it.  H,  slit 
next  to  heliostat ;  0,  pro- 
jecting lens;  P,  prism;  S, 
Si,  scale  marked  with  wave 
lengths ;  D,  Dlf  diaphragm, 
including  a  variable  slit ;  c, 
GI,  collecting  lens ;  E,  posi- 
tion of  object  subjected  to 
the  rays.  The  spectrum 
ranges  from  A  =  0.75  ^  to  A  = 
40  n.  (From  REINKE,  '84.) 

front  of  the  diaphragm  is  placed  a  scale  S,  Sl  of  wave  lengths  fitted  to  the 
spectrum  obtained.  Such  a  scale  may  be  constructed  with  reference  to  the 
position  of  FRAUENHOFER'S  lines  by  interpolation  from  Fig.  40.*  To  in- 
clude rays  whose  wave  lengths  differ  by  exactly  0.05  /x  the  slit  must  be  wider 
when  at  the  blue  end  than  when  at  the  red  end  of  the  spectrum  (Fig.  40). 

to  form  a  hollow,  triangular  (60°)  prism.  The  plates  are  fixed  to  each  other 
and  to  the  glass  base  by  a  pasty  cement  made  by  mixing  plaster  of  paris  and 
liquid  glue.  This  cement  soon  hardens,  and  is  not  attacked  by  the  carbon 
disulphide.  The  hollow  prism  is  now  filled  with  fluid,  and  a  triangular  glass 
plate  is  cemented  on  as  a  cover. 

*  If  artificial  light  is  used,  two  points  on  the  scale  can  be  obtained  as  follows  : 
Volatilize  in  a  Bunsen  flame,  temporarily  replacing  the  lamp,  a  salt  of  barium 
and  one  of  calcium,  and  note  the  position  of  the  extreme  blue  band  on  the  former 
(line  F)  and  the  yellow  band  of  the  latter  (line  D).  After  determining  these 
two  points  the  remaining  lines  can  be  plotted  upon  the  scale. 


1-1] 


APPLICATION  AND  MEASUREMENT  OF  LIGHT 


157 


A  second  method  of  getting  monochromatic  light  is  by  the 
use  of  flames  tinged  with  various  volatilized  metals.  Of  these, 
lithium  salts  give  reds  at  X  =  0.67/*  and  X  =  0.61/z,,  sodium  salts 
give  a  pure  yellow  light  of  X  =  0.59/>t,  thallium  salts  (poisonous 
vapor)  a  green  at  about  X  =  0.54/z,  and  indium  salts  a  blue  and 
a  violet,  both  beyond  A  =  0.46//,.  The  number  of  metallic 
vapors  which  give  even  nearly  monochromatic  light  is,  however, 
not  large. 

A  third  method  for  producing  monochromatic  light  is  found 
in  the  use  of  solutions  of  pigments.  Such  solutions  may  be 
held  in  deep  glass  vessels  whose  back  and  front  glass  surfaces 
are  parallel  and  near  together.  In  the  following  table  are  given 
in  the  first  column  the  names  which  may  be  applied  to  differ- 
ent parts  of  the  spectrum,  following  HELMHOLTZ  (Handbuch, 
p.  251);  in  the  second  column  the  pigments  which  while  dry 
give  corresponding  spectral  colors  in  diffuse  daylight  and  which 
may  also  be  used  in  making  solutions ;  and  in  the  third  column 
certain  pigments  which  in  solution  YUNG  ('78,  p.  251)  found  to 
transmit  almost  exclusively  the  part  of  the  spectrum  named  in 
the  first  column. 

TABLE   XYII 


From  outer  limit  to  line  C,  red  .  .  . 
(  orange   . 

Cinnibar,  HgS 
(vermilion) 
Minium 

Alcoholic  solution  f  uchsin  * 

C       to        D,\ 

(  golden  yellow  .  .  . 

{  yellow   .  . 

Litharge,  PbO 
Chrome  yellow 

Concen.  Sol.  potassic  chromate 

D      to       E,\  y  ;: 
1  yellow-green  .... 

E       to          6,    green  

PbO,CrO2 
cupric  arsenite 

(a  little  red  and  green) 
Nickel  nitrate,  NiO2(NO2), 

6         to         F,    transition        from 
blue-green  to  blue 
F       to  F$G,    cyaniteblue  .... 
F$  G  to        G,    indigo  blue  

SCHEEL'S  green 

Berlin  blue 
Ultramarine 

Bleu  de  Lyon  (a  little  V)  t 

G        to        H,    violet  

Violet  de  Parme 

Solutions  made  up  from  these  pigments  should,  however,  be 
examined  spectroscopically  before  using  to  make  sure  of  the 
purity  of  the  color. 

*  Also  a  solution  of  iodine  in  carbon  disulphide.     (PRINGSHEIM,  '80,  p.  409.) 
t  F  to  H  is  given  by  ammoniated  copper  sulphate,  CuSo44  NH3  +  H20 
(PRIXGSHEIM). 


158  LIGHT  AND   PROTOPLASM  [Cn.  VII 

Finally,  a  fourth  and  decidedly  practical  way  of  obtaining 
pure  colors  is  by  the  use  of  transparent  plates  of  colored  glass  or 
other  transparent  solids.  It  is  very  difficult  to  get  monochro- 
matic glasses  of  certain  colors  in  the  market.  A  pure  red  is 
easily  obtainable;  the  blue  is  apt  to  contain  some  red  also  ;  and 
the  green,  both  blue  and  yellow.  Lord  RAYLEIGH  ('81,  p.  64) 
has  used  "  films  of  gelatine  or  of  collodion,  spread  upon  glass 
and  impregnated  with  various  dyes,  gelatine  being  chosen  when 
the  dye  is  soluble  in  water  and  collodion  when  the  dye  is  soluble 
in  alcohol."  This  method  seems  to  me  to  be  of  wide  applica- 
bility in  our  light  experiments.  For  solid  media  are,  after  all, 
far  less  troublesome  than  fluids,  vapors,  or  spectra ;  and  con- 
venience is  one  of  the  most  valuable  qualities  of  a  method. 

A  brief  statement  must  be  made  concerning  the  physical 
properties  of  the  different  light  waves.  An  inspection  of  any 
prismatic  solar  spectrum  shows  that  certain  parts  are  brighter 
to  our  eyes  than  others,  and  a  thermometer  placed  in  different 
parts  of  the  spectrum  indicates  a  higher  temperature  towards 
the  red  end.  Curves  are  given  in  Fig.  42  which  show  the 
relative  warmth  of  different  parts  of  the  visible  spectrum  both 
when  the  spectrum  is  a  normal  one  (i.e.  such  as  is  given  by  a 
diffraction  grating,  where  all  rays  differing  in  wave  length  by 
O.I//,  are  equally  distant)  and  when  it  is  prismatic  (in  which 
there  is  a  crowding  of  rays  at  the  red  end).  Curves  of  relative 
brightness  and  of  relative  chemical  (actinic)  activity,  so  far  as 
can  be  judged  from  the  union  of  chlorine  and  hydrogen,  are 
also  given,  for  the  prismatic  spectrum.  Being  laid  off  on  the 
"  normal "  scale  the  curves  last  mentioned  are  somewhat  dis- 
torted. From  these  curves  it  appears  that  the  brightest  part 
of  the  spectrum  lies  between  lines  D  and  E,  at  X= 0.59 /,<,;*  the 
warmest  part  is,  in  the  normal  spectrum,  near  X=  0.60/>c,  but 
in  the  prismatic  spectrum,  beyond  the  visible  red,  at  about 
X  =  1.00/A.  Finally,  the  chemical  activity  of  the  rays  increases 
towards  the  blue  end  of  the  spectrum,  but  the  relative  activity 
is  different  for  the  different  substances  acted  upon.  Measured 
by  their  ability  to  unite  chlorine  and  hydrogen,  the  rays  having 

*  MENGARINI  ('89,  p.  135)  finds  the  point  of  maximum  brightness  to  lie  at 
about  0.57  M. 


§1] 


APPLICATION  AND  MEASUREMENT  OF  LIGHT 


159 


1                                                                  1 

( 

Jurve  of  Relative  Warmth  in  Normal  Spectrum. 

Curve  of  Relative  "Warmth  in  Prismatic  Spectrum. 

Curve  of  Relative  Actinic  Effect  in  Prismatic  S 

jectrum. 

3 

L^- 
V_ 

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FIG.  42.  —  Scale  of  normal  solar  spectrum,  above  which  is  drawn  the  normal  curve 
of  relative  warmth ;  also  the  curves  of  relative  warmth,  brightness,  and  actinism 
of  the  prismatic  solar  spectrum.  The  curves  of  warmth  are  taken  from  LAXGLEY 
('84,  p.  233) ;  the  curve  of  brightness  is  constructed  from  the  data  of  VIKRORDT 
(73,  p.  17) ;  that  of  actinism  is  taken  from  BUXSEX  and  ROSCOE  ('59,  p.  268)  and 
indicates  the  relative  efficiency  of  the  different  rays  of  the  midday  sun  in  caus- 
ing the  union  of  chlorine  and  hydrogen.  The  absolute  value  of  the  ordinates  is 
entirely  arbitrary. 

a  longer  wave  length  than  0.51//,  have  feeble  chemical  action  ; 
at  about  X  =  0.42//,  this  action  reaches  a  maximum. 

Not  only  the  quality  but  also  the  intensity  of  the  light  with 
which  we  experiment  must  be  known.     It  is,  fortunately,  quite 


160  LIGHT   AND  PROTOPLASM  [Cn.  VII 

easy  to  determine  the  intensity  of  white  light  in  terms  of  a 
recognized  unit ;  namely,  a  paraffine  candle  burning  at  the  rate 
of  7.78  grammes  per  hour.  A  paraffine  candle  burning  at  this 
rate  has  one  candle  power  (C.  P.) ;  burning  at  twice  this  rate, 
2  candle  power,  and  so  on.  A  comparison  of  any  other  light 
with  this  standard  may  be  made  by  means  of  any  of  the  well- 
kiiown  photometers,  of  which  text-books  of  physics  give  a 
description. 

The  determination  of  the  intensity  of  a  colored  light  requires 
an  additional  piece  of  apparatus  ;  namely,  a  spectrophotometer. 
The  two  principal  types  of  spectrophotometer  are  that  of 
VIERORDT  (73)  and  that  of  GLAN  ('77),  both  of  which 
have  undergone  important  improvements.  The  principle  in 
both  types  is  the  same.  A  spectrum  of  both  the  unmodified 
(standard)  light  and  that  which  has  passed  through  the  colored 
screen  are  made  side  by  side,  so  that  their  corresponding  colors 
can  be  compared.  Since  the  source  of  light  is  the  same,  every 
part  of  the  spectrum  of  the  unmodified  light  will  be  brighter  than 
the  corresponding  part  of  the  spectrum  of  the  colored  light. 
To  bring  the  corresponding  colors  in  the  two  spectra  to  the 
same  intensity,  the  unmodified  light  must  be  made  less  intense 
to  a  measurable  extent.  In  VIERORDT'S  spectrophotometer 
this  result  is  brought  about  by  narrowing  that  half  of  the  slit 
through  which  the  unmodified  light  passes  to  get  to  the  prism. 
In  GLAN'S  apparatus  the  diminution  in  intensity  is  gained  by 
the  polarization  of  both  lights  and  the  obscuring  of  the  brighter 
by  the  rotation  of  its  analyzing  NICHOL  prism,  until  equality 
of  brightness  is  obtained.  A  modified  form  of  VIERORDT'S 
convenient  instrument  is  made  by  H.  KRUSS  of  Hamburg, 
Germany.  A  modified  form  of  GLAN'S  photometer  is  de- 
scribed by  VOGEL  ('77). 

VOGEL'S  apparatus  (Fig.  43)  consists  essentially  of  a  collimator  contain- 
ing (1)  a  slit  of  changeable  width,  separated  by  a  band  q  into  an  upper  and 
a  lower  part  to  receive  respectively  the  modified  and  the  normal  light ;  (2)  a 
lens  to  render  the  rays  parallel  before  they  impinge  upon  (3)  a  doubly  refract- 
ing quartz  prism,  by  which  both  upper  and  lower  rays  are  broken  into  two 
polarized  rays.  Of  these  four  rays  the  uppermost  and  the  lowest  are  cut 
off  by  a  diaphragm  near  F,  so  that  only  the  middle  two,  which  lie  near 
together,  pass  eventually  to  the  eye.  These  two  rays  are  oppositely  polar- 
ized and  come,  one  from  the  upper,  the  other  from  the  lower  slit.  The  two 


CHEMICAL   ACTION  OF   LIGHT 


161 


rays  now  pass  through  (4)  a  XICHOL  prism  (capable  of  being  rotated  along- 
side a  graduated  arc)  set  at  45°,  in  which  position  both  rays  pass  through 
j-^l  without  changed  relative  intensity.  The  rays  emerging  from 
J)  |L  the  collecting  telescope  are  now  dispersed  by 

P_j   j  ^&      passing  through  the  vertically  placed  prism, 

and  the  adjacent  parallel  spectra  are  observed 
through  a  telescope.  By  a  rotation  of  the 
XICHOL  prism  through  an 
observed  number  of  degrees 
the  stronger  light  may  be 
brought  to  the  intensity  of 
the  weaker.  The  relative 
intensity  of  two  lights  with 
reference  to  a  third  (con- 
stant) is  as  the  squares  of 
the  tangent  of  the  angle 
through  which  the  NICHOL 
prism  has  been  rotated. 
Other  modifications  of 

GLAN'S  photometer  are  those  of  Lord  RAYLEIGH  ('81)  and 
of  LEA  ('85),  upon  which  the  spectrophotometer  of  the 
Cambridge  (Eng.)  Scientific  Instrument  Co.  is  based. 


FIG.  43.  —  Diagrams  showing  con- 
struction of  VOGEL'S  spectropho- 
tometer. 1.  Horizontal  section 
through  the  optical  axis.  M, 
mirror  to  reflect  standard  light, 
by  aid  of  a  totally  reflecting 
prism  p,  into  the  optical  axis. 
S,  shutter  with  slit  divided  into 
an  upper  and  a  lower  half  by 
means  of  a  band  q ;  C,  colli- 
mating  lens.  D,  doubly  refract- 
ing quartz  prism;  m,  m,  the 
holder  of  the  NICHOL  prism  X, 
which  can  be  rotated  through  an 
arc  that  can  be  read  off  from  a 
graduation  on  m,  m;  P,  a  flint 
glass  prism ;  B,  F,  0,  observing 
telescope,  in  which,  at  the  focal 
point,  near  F,  is  a  diaphragm 
cutting  out  the  two  outermost  of 
the  four  spectra  coming  through 
B.  2.  Front  view  of  the  shutter. 
(From  VOGEL,  '77.) 


§  2.    THE  CHEMICAL  ACTION  OF 
LIGHT  UPON  NON-LIVING  SUB- 

STANCES 

The  process  of  photography  has 
made  us  familiar  with  the  fact 
that  daylight  acts  upon  the  halo- 
gen salts  of  silver,  gold,  platinum, 
and  other  metals,  although  the 
nature  of  the  chemical  change 
wrought  by  the  light  is  uncer- 
tain. It  is  not,  perhaps,  gener- 
ally appreciated,  but  it  is  well 
known  to  chemists,  that  light 
can  produce  or  further  very 
many  chemical  changes,  particu- 
larly among  organic  compounds. 
The  effects  are  mainly  due  to  the 
blue  and  violet  rays,  hence  are 


162  LIGHT   AND   PROTOPLASM  [Cn.  VII 

not  the  results  of  the  heat  of  sunlight.  Most  of  these  chemi- 
cal effects  may  be  grouped  under  four  heads.  1.  Synthetic ; 
2.  Analytic ;  3.  Substitutional ;  and  4.  Isomerismic  and  Poly- 
mer ismic.  A  few  others  may  be  classed  (5)  as  fermentative. 
Let  us  now  consider  each  of  these  five  classes.* 

1.  The  Synthetic  Effects  of  Light  will  be  considered  chiefly 
with  reference  to  organic  compounds.  All  the  cases  I  have 
gathered  fall  into  three  groups  :  addition  to  the  organic  com- 
pound either  (a)  of  oxygen,  (/3)  of  chlorine  or  bromine,  or 
(7)  of  another  organic  compound. 

Among  the  compounds  which  take  up  oxygen  is  bilirubin, 
C32H36N4O6,  a  solution  of  which,  in  sunlight,  even  when  air  is 
excluded,  oxidizes  to  biliverdin,  C32H36N4O8.  In  the  absence 
of  sunlight  this  change  requires  air  (B.  Ill,  418).  DUCLAUX 
('87,  p.  353)  finds  that  vegetable  oils,  such  as  olive  or  palm 
oils,  are  rapidly  oxidized  if  exposed  to  light.  CHASTAIGN  ('77, 
p.  198)  believes  this  oxidizing  action  of  light  upon  organic  com- 
pounds to  be  of  very  wide-spread  occurrence ;  the  blue-violet 
part  of  the  spectrum  being,  in  this  respect,  the  most  active. 

The  direct  combination  by  means  of  light  of  a  halogen  and 
another  substance  is  also  not  rare.  Thus,  in  daylight,  hydro- 
gen unites  with  chlorine  explosively.  It  unites  with  bromine 
also,  although  with  difficulty.  Similarly,  equal  volumes  of 
chlorine  and  carbon  monoxide  unite  quickly  in  the  sunlight  or 
magnesium  light  to  form  carbon  monoxid  chloride,  COC12 
(B.  I,  546).  Again,  when  chlorine  is  passed  through  alcohol 
under  the  influence  of  strong  sunlight  or  magnesium  light  the 
two  substances  unite  and  produce  chloral  hydrate  (STREET  and 
FRANZ,  '70).  Likewise,  when  chlorine  is  passed,  in  sunlight, 
through  a  solution  of  C3H2C12O2  in  CS2,  there  is  formed 
C3H2C14O2,  two  atoms  of  Cl  having  been  added.  Finally, 
C2C16  may  be  made  by  uniting  C2C14  and  C12  in  sunlight  (B.  I, 
158)  ;  and  the  compound  C2H4  •  FeBr2  •  2H2O  may  be  made  by 
passing,  in  sunlight,  C2H4  through  a  concentrated  aqueous 
solution  of  FeBr2  (B.  I,  113). 

*  Most  of  these  cases  were  obtained  by  searching  through  BEILSTEIX  ('86-'93). 
References  to  this  book  will  be  made  throughout  this  section  by  the  letter  B, 
followed  by  the  number  of  the  volume  and  page  upon  which  the  statement  may 
be  found. 


§  2]  CHEMICAL   ACTIOX  OF   LIGHT 

Important  cases  of  the  direct  synthesis  of  organic  compounds 
are  given  by  KLIXGER  and  STANDKE  ('91).  These  authors 
have  shown  that  in  sunlight  (and  not  in  the  dark)  phenanthren- 
chinon  unites  directly  with  benzaldehyd  to  form  a  third  com- 
pound phenanthrenhydrochinonmonobenzoat,  in  accordance 
with  the  formula  :  C14H8O2  +  C6H5CHO  =  C14H8  (OH) 
(O  •  CO  C6H5).  Again,  chinon  (benzochinon)  and  benzaldehyd 
may  unite  in  the  sunlight  to  form  benzohydrochirion,  according 
to  the  formula :  C6H4O2  +  C6H5CHO  =  C6H5CO  C6H3(OH)2. 
Finally,  benzochinon  and  isovaleraldehyd  may  similarly  unite 
to  form  isovalerochinhydron,  thus  :  C6H4O2  4-  C4H9CHO  = 
C4H9CO  C6H3(HO)2.  These  cases,  then,  are  examples  of 
organic  compounds  which  are  wholly  indifferent  in  the  dark, 
but  which,  subjected  to  strong  sunlight,  lose  their  identity  by 
uniting  directly;  they  may  suffice  to  illustrate  the  important 
synthetic  effect  of  sunlight  on  non-living,  organic  compounds. 

2.  Analytic  Effect  of  Light.  —  Cases  of  this  effect  are  nu- 
merous, varied,  and  striking.  I  will  cite  a  few.  The  organic 
dibasic  acids  CnH2n_2O4  break  up  in  the  sunlight  and  in  the 
presence  of  a  small  quantity  of  uranium  oxide,  into  CO2  and 
an  acid  CnH2nO2  (B.  I,  63).  For  example,  oxalic  acid,  C2H2O4, 
breaks  up  thus  into  formic  acid,  CH2O2  and  CO2.  Also  an 
aqueous  solution  of  butyric  acid,  C4H8O2,  in  the  presence  of 
uranyl  nitrate,  breaks  up,  in  the  sunlight,  into  CO2  and 
C3H8  (B.  I,  422).  We  have  seen  that  chlorine  will  unite 
directly  with  organic  compounds  under  the  influence  of  light ; 
on  the  other  hand,  compounds  containing  chlorine  may  lose  it 
in  the  sunlight.  Thus  under  these  conditions  the  ketone 
(C8H17XO  •  HCl)2PtCl4,  an  ammoniacal  derivative  of  acetone, 
becomes  (C8H1TNO  •  HCl)2PtCl2;  and  (C9H17XO  -  HCl)2PtCl4 
becomes  (C9H17XO  -  HCl)2PtCl2  (B.  I,  982,  983).  Again,  chlo- 
rine acetate,  Cl  •  O  •  C2H3O,  undergoes  slow  decomposition,  in 
the  light  (B.  I,  462)  ;  C5H6C12,  a  derivative  of  pentine,  C5H8, 
does  the  same  ;  and  ethylester,  CIO  •  C2H5,  explodes  in  sunlight. 
Similarly  explosive  in  sunlight  is  the  greenish  oil  distilled  when 
absolute  alcohol  is  poured  over  dry  calcium  chloride  (B.  I,  223). 
Finally,  sugar  (DUCLAUX,  '86,  p.  881)  and  oxalic  acid  (DcrwxES 
and  BLUXT,  '79,  p.  209)  are  oxidized  and  break  up  into  water, 
carbon  dioxide,  and  other  compounds.  These  cases  may  serve 


164  LIGHT  AXD  PROTOPLASM  [Cn.VIl 

to  show  the  important  chemical  effects  of  sunlight  in  the  dis- 
integration of  organic  compounds. 

3.  Substitution  Effects   of   Light.  —  The  principal  substitu- 
tion effect  of  light  is  the  replacement  of  hydrogen  in  an  organic 
compound  by  either  chlorine  or  bromine.     This  occurs  so  fre- 
quently that  examples  are  superfluous.     The  substitution  takes 
place  most  rapidly  and  completely  in  direct  sunlight,  and  it  has 
been  shown  that  the  rays  at  the  blue  end  of  the  spectrum  are 
the   most   active   in   this   process.      The   compounds   affected 
belong  to  the  most  varied  groups  of  both  the  fatty  and  aro- 
matic  series  —  carbohydrates,  acids,   aldehydes,  ketones,    and 
sulphides. 

4.  The  Isomerismic  and  Polymerismic  Changes  produced  by 
Light  are  among  the  most  interesting.     I  will  cite  some  exam- 
ples.    In  the  first  place,  it  may  be  said  that  the  changes  in  the 
elements  phosphorus  and  sulphur  by  which  they  assume  their 
red  form  have  been  ascribed  to  sunlight.     Elseomargin  acid, 
C17H30O2,  is  a  compound  found  in  connection  with  glycerine 
in  the  oil  of  the  seeds  of  Eleeococca   (Aleurites)   vernica  — 
Chinese  oil  tree  —  one  of  the  Euphorbiacese.     This  acid  crys- 
tallizes in  rhombic  plates  which  melt  at  48°.     When  an  alco- 
holic solution  of  this  acid  is  placed  in  a  bright  light,  leaf -like 
crystals  of  its  isomere,  elseostearin  acid,  which  melt  at  71°, 
are  produced  (B.  I,  535).     Again,  thymochinon  forms  yellow 
crystals,  which  are  soluble  in  alcohol.     Subjected  to  a  strong 
light,  opaque,  whitish-yellow  crystals  are  produced,  which  are 
insoluble  in  alcohol.     This  substance,  which  does  not  arise  in 
the  dark,  and  is  hence  not  merely  the  result  of  oxidation,  is 
called   polythymochinon    (B.    Ill,  180).      Again,   among   the 
derivatives  of  ethylene,  C2H4,  is  chlorethylene,  C2H3C1,  a  gas. 
When  placed  in  the  sunlight  this  passes  into  a  polymere,  which 
forms  a  viscous,  amorphous,  insoluble  mass  (B.  I,  158).      In 
like  fashion,  bromethylene,  C2H3Br,  a  fluid,  is  rapidly  trans- 
formed in  the  sunlight  into  a  polymere,  which  is  solid,  amor- 
phous, and  insoluble  in  water,  alcohol,  or  ether  (B.  I.  181),  and 
bromacetylen,  C2HBr,  a  gas,  is  gradually  transformed,  in  the 
light,  into  a  solid  polymere.     Finally,  very  many  substances 
undergo  a  gradual  change  of  color  in  the  sunlight,  but  the 
nature  of  the  accompanying  molecular  change  is  unknown. 


§2]  CHEMICAL   ACTIOX  OF   LIGHT  165 

5.  Changes  resembling  those  brought  about  by  fermentation 
are  produced  by  light.  Thus  NIEPCE  DE  SAINT  VICTOR  and 
CORVISART  ('59)  have  found  that  a  0.1%  solution  of  starch, 
exposed  during  6  to  18  hours  to  the  summer  sun,  becomes  trans- 
formed into  sugar,  while  in  the  dark  no  such  change  occurs. 
The  change  is  favored  by  a  small  quantity  of  uranium  nitrate. 
In  a  similar  fashion  glycogen  is  transformed  into  sugar  more 
rapidly  in  the  light  than  in  the  dark.  On  the  other  hand, 
GHEEX  ('94)  finds  that  the  ferment  which  normally  transforms 
starch  into  sugar  is  destroyed  by  subjection  to  a  strong  light, 
the  ^iolet  rays  being  especially  active  in  this  process.  Like- 
wise, ptyalin,  the  ferment  of  saliva,  is  destroyed  by  light. 

To  sum  up,  light  affects  organic  compounds  in  very  varied 
and  important  ways.  We  are,  accordingly,  prepared  to  find 
that  light  exerts  a  very  important  influence  on  the  activities 
of  protoplasm.  Nor  is  the  influence  necessarily  confined  to 
the  surface,  for  most  protoplasmic  bodies  are  more  or  less 
translucent.  Thus  SACHS  ('60)  found  by  looking  through 
a  tube  with  one  end  fitted  to  the  eye  and  the  other  directed 
towards  the  sunlight,  that  considerable  layers  of  plant  tissue, 
for  example  over  32  mm.  of  the  tissue  of  the  potato  tuber,  did 
not  cut  out  all  the  light,  and  that  red  had  the  greatest  pene- 
trating power,  violet  the  least.  Even  the  epidermis  of  man 
permits  light  to  pass,  and  ONIMUS  ('95)  asserts  that  light  can 
pass  through  the  hand  to  such  an  extent  as  to  affect  during 
26  to  30  minutes  an  orthochromatic  plate  kept  in  a  tight  wooden 
box  perforated  only  by  the  opening  which  is  covered  by  the 
hand.  Whether  the  "  RONTGEN  rays,"  which  have  so  striking 
a  power  of  penetrating  organic  matters,  are  more  of  the 
nature  of  light  than  of  other  physical  agents,  is  still  a  subject 
of  debate.  Whether  they  produce  any  important  chemical 
changes  in  protoplasm  has  not  yet  been  fully  determined.* 

*  During  the  six  months  which  have  elapsed  since  the  above  was  written, 
accounts  of  marked  physiological  effects  of  the  ROXTGEN  rays  have  been  pub- 
lished. Thus,  exposure  of  the  skin  to  them  for  an  hour  frequently  causes  loss 
of  hair  and  finger  nails,  and  produces  symptoms  resembling  those  of  sunburn. 
AXENFELD  (Centralbl.  f.  Physiol.  X,  147)  finds  that  many  insects  and  a  crusta- 
cean, Porcellius,  kept  in  a  box  only  one-half  of  which  is  penetrated  by  the  rays, 
aggregated  in  this  part.  Several  experiments  upon  the  tropic  influences  of  the 
rays  have  resulted  negatively. 


166  LIGHT  AND   PROTOPLASM  [Cn.  VII 

§  3.   THE  EFFECT  OF  LIGHT  UPON  THE  GENERAL  FUNCTIONS 
OF  ORGANISMS 

In  this  section  we  shall  consider  in  succession  (1)  the  effect 
of  light  upon  metabolism ;  (2)  the  vital  limits  of  light  action 
on  protoplasm ;  and  (3)  the  effect  of  light  upon  the  movement 
of  protoplasm. 

1.  Effect  of  Light  upon  Metabolism  (including  Assimilation). 
—  Metabolism  is  a  complex  of  chemical  processes.  Since,  as 
we  have  already  seen,  light  has  important  chemical  effects,  we 
are  not  surprised  to  find  that  it  plays  an  important  ^ole  in 
metabolism.  The  effects  of  light  are,  however,  of  two  distinct 
kinds.  One  is  a  thermic  effect,  due  to  the  heat  rays  of  white 
light ;  the  other  is  a  chemical  effect  due  to  the  "  actinic  rays  V 
of  the  spectrum. 

a.  The  Thermic  Effect  of  Light  on  Metabolism  is  shown  chiefly 
in  the  assimilative  processes  of  chlorophyllaceous  plants.  The 
facts  of  this  assimilation  are  chiefly  these  :  various  simple  com- 
pounds, water,  carbon  dioxide,  salts  of  ammonia  and  nitrates, 
are  used  as  food  by  plants.  For  every  volume  of  the  gas  — 
carbon  dioxide  —  taken  in,  one  volume  (nearly)  of  oxygen  is 
excreted.  Starch  (C6H10O5)  is  the  first  visible  product  of  the 
water  and  carbon  dioxide  taken  in.  Chlorophyll  is  essential  to 
the  absorption  of  carbon  dioxide,  to  the  giving  forth  of  oxygen, 
and  to  the  formation  of  starch.  Finally,  chlorophyll  can  as- 
similate only  in  the  presence  of  sunlight  and  at  a  proper  tem- 
perature. 

Now,  not  all  the  rays  of  sunlight  with  their  varied  wave 
lengths  are  essential  to  this  process.  Just  what  rays  are 
the  essential  ones  has  been  a  point  of  some  dispute.  The 
earlier  studies  on  the  subject,  made  chiefly  by  DRAPER  ('44), 
SACHS  ('64),  and  PFEFFER  ('71),  were  unanimous  in  declaring 
that  the  most  active  rays  in  assimilation  were  those  occupying 
the  yellow  part  of  the  spectrum  at  about  line  D  —  the  region 
of  maximum  brightness  to  our  eyes  (Fig.  42).  But  these  ob- 
servers were  at  fault  in  that,  while  they  carefully  determined 
the  quality  of  light  and  the  corresponding  quantity  of  assimila- 
tion, none  of  them  gave,  in  the  experiments  with  color  screens, 
any  adequate  data  upon  the  intensity  of  the  diversely  colored 


EFFECT  UPON  GENERAL  FUNCTIONS 


167 


lights  employed ;  and  this  is  a  fundamental  matter,  for  it  has 
been  shown,  for  instance  by  REIXKE  ('83  and  '84),  that,  within 
certain  limits,  the  rate  of  assimilation  increases  with  the  inten- 
sity of  the  light  (Fig.  44).  Even  in  experiments  with  the 
colors  of  prismatic  spectra  one  must  remember  that  the  rays 
are  crowded  together  at  the  red  end,  so  that  a  given  length  of 
the  spectrum  contains  more  rays  at  that  end  than  at  the  other 
(of.  Fig.  40). 

Later  investigations  with  improved  methods  have  shown 
quite  conclusively  that  it  is  especially  the  rays  with  X  =  0.68/4, 
or  those  very  close  to  the  absorption  band  B,  which  are  most 


FIG.  44.  —  Curve  showing  the  relation  between  intensity  of  light  (abscissae)  and  quan- 
tity of  oxygen  set  free  by  Elodea  canadensis.  i  indicates  the  unit  intensity  of  the 
light  from  the  heliostat.  (From  REINKE,  '84.) 

active  in  assimilation.  The  methods  employed  have  been  most 
diverse,  but  they  have  yielded  the  same  result.  TIMIRIAZEFF 
('77)  studied  the  assimilative  power  of  the  different  parts 
of  the  solar  prismatic  spectrum,  determining  by  gasometric 
methods  the  quantity  of  gases  decomposed  in  a  given  time. 
REINKE  ('84)  also  used  the  spectrum,  but  by  means  of  his 
spectrophor  was  able  to  get  more  strictly  monochromatic  light, 
to  use  more  nearly  comparable  extents  of  the  spectrum,  and, 
especially,  to  get  a  more  exactly  comparable  (in  this  case, 
optimum)  assimilative  intensity  for  each  part  of  the  spectrum 
than  his  predecessors.  (See  p.  156.)  As  the  measure  of 
assimilation,  REIXKE  used  the  number  of  gas  bubbles  set  free 


168 


LIGHT   AND   PROTOPLASM 


[Cii.  VII 


per  minute  by  the  submerged,  illuminated  plant.     As  is  shown 
in  Fig.  45,  the  maximum  of  gas  production  occurred  at  about 

absorption  line  B  —  and  this 
is  the  more  marked  of  the 
absorption  bands  of  chloro- 
phyll. 

A  similar  result  was  reached 
by  ENGELMANN  and  set  forth 
in  a  long  series  of  papers  ('81, 
'82,  '82a,  '83,  '83a,  '84,  '86,  and 
'87).  He  found  that  certain 
bacteria  are  extremely  sensi- 
tive to  oxygen,  moving  in  the 
direction  of  small  increments 
of  the  oxygen  density.  Now, 
by  putting  a  thread  of  alga  in 
the  same  water  with  bacteria 
and  subjecting  the  thread  to 
a  "microspectrum,"  that  part 
in  which  assimilation  is  pro- 
ceeding most  rapidly,  and  in 
which,  therefore,  oxygen  is 
being  most  rapidly  excreted, 
will  be  indicated  by  the  great- 
est aggregation  of  bacteria. 
The  microspectrum  was  pro- 
duced by  means  of  an  appa- 
ratus especially  designed  by 
ENGELMANN  for  his  work  and 
now  manufactured  by  the 
ZEISS  firm  in  Jena.  The 
appearances  seen  under  the 
microscope  when  the  spec- 
trum falls  upon  the  alga  in 
the  bacterium  -  water  are 
shown  in  Fig.  46.  The  max- 
imum aggregation  (hence, 
maximum  assimilative  activ- 
ity) at  the  red  end  occurs 


I    j 

1 

j 

i    ! 

|i 

so    ]T 

X)[       '( 

50      6001       .5, 

>o 

5 

>0|        4 

>0 

it 

a 

B  C 

D 

E 

b 

1 

C 

ifc 

FIG.  45.  —  Curve  whose  ordinates  are  pro- 
portional to  the  number  of  gas  bubbles 
eliminated  per  minute  by  leaves  illumi- 
nated by  the  various  rays  whose  wave 
lengths  are  given  at  the  bottom  of  the 
diagram,  and  whose  number  of  vibra- 
tions per  second  are  given  at  the  top. 
The  background  of  the  figure  is  com- 
posed of  the  absorption  spectra  of  the 
chlorophyll  in  living  leaves.  1,  2,  etc., 
at  the  left,  indicate  the  number  of  leaves 
of  Impatiens  parviflora,  which,  when 
superimposed,  give  the  corresponding 
spectrum  at  the  right  of  these  numbers. 
The  absorption  at  0  is  from  a  fern  pro- 
thallus,  that  at  Ale  is  derived  from  an 
alcoholic  solution  of  chlorophyll.  I  to 
IV  indicate  absorption  bands.  Beyond 
F  there  is  very  general  absorption 
of  the  highly  refractive  rays.  (After 
KEINKE,  '84.) 


§3] 


EFFECT  UPON  GENERAL  FUNCTIONS 


169 


close  to  the  absorption  band  of  chlorophyll.  Observations 
upon  the  chlorophylls  of  brown,  blue-green,  and  red  cells, 
which,  as  EXGELMAXX'S  microspectro-photometer  indicated, 
have  a  maximum  absorption  at  other  points,  showed  a  maxi- 
mum of  assimilative  activity  at  these  other  absorption  points. 
In  bacterio-purpurin  also,  in  which  some  of  the  most  active 
assimilative  rays  are  those  of  the  invisible  red  at  about 
X  =  0.85/1,  most  oxygen  is  produced  at  this  point.  (ExGEL- 
MAXX,  ?83,  p.  709.) 

Finally,  by  an  ingeniously  devised  experiment,  TIMIRIAZEFF 
('90)  has  settled  this  matter  in  the  most  direct  and  indubitable 


FIG.  46. — Piece  of  Cladophora  with  swarming  bacteria  in  the  microspectrum  (gas- 
light) .  The  chlorophyll  grains  which  fill  the  cells  very  uniformly  are  omitted ; 
and,  instead,  the  absorption  band  between  B  and  C,  and  the  tolerably  pro- 
nounced band  at  the  violet  end  between  E  and  F,  are  indicated  by  shading. 
(From  EXGELMAXX,  '82.) 

fashion.  He  kept  a  plant  for  two  or  three  days  in  the  dark, 
until  the  starch  in  its  leaves  had  gone;  then,  in  a  dark  room,  a 
prismatic  spectrum  was  thrown  upon  the  leaf  and  the  position 
of  FRAUEXHOFER'S  lines  indicated  on  the  leaf.  After  from 
three  to  six  hours,  starch  had  formed,  under  the  influence  of 
the  light,  only  in  the  region  of  the  absorption  bands  of  chloro- 
phyll lying  between  B  and  D.  This  was  determined  by  plung- 
ing the  leaf  into  boiling  alcohol,  thus  decolorizing  it,  and  then 
staining  in  tincture  of  iodine,  which  combines  especially  with 
the  starch.  The  deeply  dyed  places,  where  starch  had  been 
formed,  reproduced  the  absorption  spectra  of  chlorophyll. 

The  concurrent  testimony  of  these  and  other  observers  work- 
ing upon  so  diverse  material  and  with  such  excellent  methods 


170  LIGHT   AND   PROTOPLASM  [Cn.  VII 

justifies  the  conclusion  that  it  is  the  rays  absorbed  by  the  plant 
pigments  which  enable  them  to  do  their  work  in  the  decompo- 
sition of  carbon  dioxide.  The  effective  absorbed  rays  are, 
moreover,  chiefly  those  towards  the  red  end  of  the  spectrum, 
those  having  over  525  x  1012  vibrations  per  second  (i.e.  below 
the  D  line).* 

In  conclusion  it  may  be  said  that  the  greater  proportion  of 
the  radiant  energy  entering  the  plant  tissue  is  absorbed.  Thus 
MAYER  ('93)  has  shown  that  of  dark  radiant  heat  at  100° 
about  80%  is  absorbed  by  a  leaf  through  which  it  passes,  and 
this  proportion  is  about  the  same  whether  the  leaf  is  thick  or 
thin.  Of  this  absorbed  heat  perhaps  less  than  10%  is  absorbed 
by  the  chlorophyll.  The  rest  must  be  used  up  in  the  vital 
processes  other  than  assimilation. 

b.  The  Chemical  Effect  of  Light  on  Metabolism  must  now  be 
considered;  and  of  this  we  must  notice  at  the  outset  two 
degrees.  The  greater  effect,  which  is  a  fatal  one  and  the  better 
known,  will  be  treated  of  further  on.  The  lesser  effect  is  less 
striking,  yet  it  must  be  included  in  the  greater.  It  shows 
itself  in  a  disturbance  of  metabolism. 

This  disturbance  of  metabolism  is  evinced  in  some  green 
plants  by  heightened  production  of  carbon  dioxide  and  the 
formation  of  chlorophyll ;  and  it  is  noteworthy  that  a  similar 
result  occurs  among  Infusoria,  according  to  the  observations  of 
FATIGATI  ('79),  who  finds  the  violet  rays  more  active  than  the 
green  in  this  process.  Among  the  Metazoa  light  produces  im- 
portant chemical  changes  in  the  retina  of  the  eye,  and  especially 
in  the  skin,  facilitating  the  production  of  pigment.  That  im- 
portant chemical  changes  take  place  in  the  illuminated  retina 
follows  from  the  experiment  of  placing  the  electrodes  at  oppo- 
site surfaces  of  the  frog's  retina.  The  galvanometer  shows  in 
the  darkened  eye  a  slight  "  current  of  rest  "  flowing  from  the 
front  face  to  the  deeper-lying  part,  containing  the  cones.  If 
now  the  retina  be  suddenly  illuminated  by  blue,  green,  yellow, 
red,  or  white  light,  a  current,  the  result  of  chemical  action, 
appears  flowing  in  the  opposite  direction  ;  this  continues  for 

*  Other,  less  important,  thermal  effects  of  light  on  plants  are  found  in  the 
formation  of  chlorophyll  and  in  the  quickening  of  transpiration,  which  seem, 
chiefly  due  to  the  red  and  ultra-red  rays. 


§  3]  EFFECT  UPON   GENERAL   FUNCTIONS  171 

some  time,  slowly  diminishing,  however,  in  intensity.  Certain 
chemical  changes  in  the  living  retina  may,  indeed,  be  studied 
optically.  These  especially  concern  the  visual  purple.  This 
is  a  substance  lying  in  the  outer  ends  of  the  rods  of  the  retina, 
which,  under  the  action  of  light,  becomes  bleached,  but  regains 
its  color  in  the  dark  (HELMHOLTZ,  Handb.,  pp.  265-273). 
These  facts  serve  to  indicate  that  light  may  influence  metabo- 
lism even  in  organisms  destitute  of  chlorophyll. 

'2.  Vital  Limits  of  Light  Action  on  Protoplasm.  —  We  have 
seen  above  (p.  167)  that  the  rate  of  assimilation  diminishes  in 
chlorophyllaceous  plants  with  a  diminution  in  the  intensity  of 
the  light.  At  last  a  point  is  reached  where  the  intensity  is  so 
low  that  no  further  assimilation  can  occur,  and  after  the  con- 
sumption of  the  stored-up  food-stuffs,  starvation  and  death  must 
eventually  ensue.  For  non-chlorophyllaceous  organisms,  how- 
ever, no  such  lower  limit  exists.  Many,  as  parasites  or  cave 
dwellers,  live  in  complete  darkness,  even  through  many  genera- 
tions. A  lower  vital  limit  to  the  action  of  light  exists  only  in 
the  case  of  chlorophyllaceous  plants. 

With  the  upper  vital  limit,  it  is,  however,  quite  different. 
This  is  found  in  the  most  diverse  groups.  Its  occurrence  in 
bacteria  being  of  especial  hygienic  importance,  these  organisms 
have  been  made  the  object  of  exhaustive  studies.  MONTE- 
GAZZA  (see  NICKLES,  '65)  was  perhaps  the  first  to  discover  that 
strong  light  kills  bacteria,  but  DOAVNES  and  BLUNT  ('78  and 
'79)  were  the  first  to  study  the  matter  thoroughly.  Since  their 
time,  numerous  experiments  have  been  made  upon  bacteria,  as 
well  as  the  higher  fungi.  For  literature,  see  FRAXKLAXD 
and  WARD  (*92),  and  WARD  ('93,  p.  309).  Even  the  earliest 
observers  found  that,  while  cultures  of  bacteria  reared  .in  the 
dark  rapidly  flourished,  they  not  merely  did  not  thrive  when 
subjected  to  sunlight,  but  actually  became  sterilized.  That  the 
sterilization  was  complete  was  shown  by  the  fact  that  when  the 
culture  was  placed  again  in  the  dark,  no  bacteria  developed  in 
it.  This  result  is  most  striking  when  certain  bacteria,  say  of 
the  species  Bacillus  anthracis,  are  mixed  with  gelatine  or  agar- 
agar,  poured  uniformly  over  a  glass  plate.  If  the  glass  plate 
is  then  covered  by  a  black  paper  stencil  containing  some 
character,  e.g.  the  letter  E,  and  exposed  to  a  November  sun- 


172 


LIGHT   AND   PROTOPLASM 


[Cn.  VII 


light  for  6  hours,  and  if  then  the  whole  plate  is  placed  in  a  dark 
incubator  at  20°  C.  for  48  hours,  the  bacteria  will  be  found  to 
have  developed  in  all  parts  of  the  plate  except  in  the  ^/-shaped 
area  sterilized  by  the  light  (Fig.  47).  Compare  the  earlier 
results  of  BUCHNER  ('92).  That  in  these  cases  it  is  the  light 
and  not  a  high  temperature  which  induces  the  sterilization  in 
the  illuminated  region  is  shown  by  the  fact  that  BUCHNER  ('92) 
obtained  even  more  striking  results  when  parts  of  the  culture 
plate  were  exposed  under  50  cm.  of  water,  which  cuts  off  the  heat. 


FIG.  47.  — Appearance  of  a  gelatine  culture  of  Bacillus  anthracis,  exposed  to  the  light 
over  only  the  area  E,  and  then  incubated  for  48  hours.  In  the  area  E  no  colonies 
have  developed.  (From  WARD,  '93.) 

Not  all  rays  have  this  bactericidal  property.  DOWNES  and 
BLUNT  -('78)  found  that  only  the  blue  rays  were  thus  active, 
for  behind  red  or  yellow  glass  the  bacteria  readily  developed. 
WARD  ('94)  threw  a  solar  spectrum  upon  an  agar  film  in  which 
bacteria  were  developing  in  a  dark  chamber.  He  found  that 
the  bactericidal  effect  was  greatest  in  the  region  of  the  blue- 
violet  rays  (about  X  =  0.43  JJL)  and  diminished  towards  the 
extreme  violet  arid  the  yellow,  where  it  had  almost  disappeared. 
These  facts  were  ascertained  by  incubating  the  bacteria  for  48 
hours  after  insolation,  when  certain  parts  affected  by  the  spec- 
trum were  found  to  remain  clear  (Fig.  48).  When  an  electric 


§3] 


EFFECT   UPON  GENERAL  FUNCTIONS 


173 


spectrum  (obtained  by  the  use  of  a  quartz  prism)  was  em- 
ployed, a  bactericidal  effect  was  obtained  (provided  no  glass 
intervened)  in  the  ultra-violet.  That  the  action  of  the  light 
was  not  in  these  cases  primarily  upon  the  food-film  was  shown 
by  the  fact  that  a  plate  of  sterile  agar,  exposed  behind  a  stencil 
plate,  and  then  laid  flat  on  a  film  of  dried  unexposed  spores, 
permitted  the  uniform  growth  of  the  spores,  in  the  illumined  as 


FIG.  48.  —  Plate  of  anthrax  spores,  exposed  for  5  hours  to  the  solar  spectrum  in 
August,  and  incubated  for  48  hours.  The  horizontal  line  shows  the  length  of 
the  spectrum.  The  vertical  lines  are  not  FRAUENHOFER'S  lines,  but  serve  to 
show  the  limits  of  the  principal  regions  of  the  spectrum.  The  clearest  area  is 
that  where  fewest  spores  have  developed  in  the  incubation  —  where,  consequently, 
the  bactericidal  effect  was  greatest.  (From  WARD,  '94.) 

well  as  in  the  unillumined  region.  All  these  observations  show 
that  the  bactericidal  action  of  light  is  due  to  the  action  of  the 
chemical  rays  on  the  protoplasm. 

Another  fact  of  importance,  first  discovered  by  DOWNES  and 
BLUNT,  is  that  light  has  no  effect  upon  bacteria  when  they  are 
in  a  vacuum.  This  abundantly  confirmed  observation  indicates 
that  death  only  secondarily  results  from  light.  The  primary 
cause  of  death  is  an  oxidation  process,  —  a  process  rendered 
possible  by  the  mediation  of  light.  As  we  have  seen  (p.  162), 
many  organic  compounds  undergo  oxidation  in  the  highly 
refracted  light  rays.  Probably  there  are  in  bacteria  such  com- 


174  LIGHT   AND  PROTOPLASM  [Cn.  VII 

pounds,  the  rapid  oxidation  of  which  is  incompatible  with  life. 
In  any  case  it  is  clear  that  the  bactericidal  effect  of  light  is  a 
chemical  one. 

Concerning  the  range  of  organisms  which  are  thus  affected, 
it  must  .be  said  that  chiefly  pathogenic  species,  such  as  the 
bacteria  of  anthrax,  of  typhus  fever,  and  of  cholera  have  been 
experimented  with  and  have  shown  themselves  most  suscep- 
tible. Other  bacteria  are,  however,  likewise  affected.  Among 
the  other  fungi,  WETTSTEIN  ('85)  found  that  the  conidia  of 
Rhodomyces  Kochii,  a  human  intestinal  parasite,  did  not  de- 
velop in  the  light.  KLEIN  ('85)  found  the  same  thing  to  be 
true  for  the  conidia  of  Botrytis  cinerea,  and  showed  that  the 
blue-violet  rays  were  the  most  effective  ones.  ELVING  ('90,  p. 
105)  gained  similar  results  with  Aspergillus,  although  several 
days  or  weeks  of  insolation  did  not  kill  the  fully  ripe  spores. 
WARD  ('93)  determined  that  insolated  spores,  cultivated  on 
agar  or  gelatine  plates,  of  Oidium  lactis  (5  cases),  Saccharomyces 
pyriformis  (4  cases),  and  "  a  4  Stysanus '  conidial  form  "  found 
as  a  saprophyte  on  the  screw-pine,  Pandanus,  (2  cases)  became 
injured.  These  are  all  hyaline  and  colorless  except  Stysanus, 
which  is  nearly  so.  Certain  colored  spores  which  WARD  experi- 
mented with  gave  negative  results,  and  WARD  concluded  that 
this  is  because  the  blue  end  of  the  spectrum  is  cut  off  before 
reaching  the  deeper  protoplasm.  However  this  may  be,  we 
actually  find  that  in  many,  but  not  all,  fungi  the  metabolic 
processes  of  the  spores  are  disturbed  and  even  death  is  pro- 
voked by  intense  light. 

Why  the  spores  should  be  especially  susceptible  to  the  action 
of  light  is  an  important  inquiry.  WARD  believes  the  answer 
to  be  that  the  spores  contain  oily  substances,  which  are  espe- 
cially liable  to  oxidation  in  light,  as  we  have  already  seen. 

Finally,  we  have  to  consider  the  experiments  which  demon- 
strate that  a  strong  sunlight  may  be  injurious  even  to  green 
plants.  This  result  follows  clearly  from  the  work  of  PRINGS- 
HEIM  ('81).  When  strong  sunlight  is  focussed  for  a  short  time 
upon  cells  of  Spirogyra,  Nitella,  Mesocarpus,  or  Tradescantia 
stamen  hairs  in  atmospheric  air  (5  to  15  minutes),  they  are 
killed.  No  result  occurs,  however,  when  the  same  light  falls 
upon  green  cells  in  which  the  atmosphere  has  been  replaced  by 


§3] 


EFFECT   UPON  GENERAL   FUNCTIONS 


175 


=  •= 


hydrogen  (Fig.  49).  That  it  is  here  also  the  oxygen  (and  not 
the  carbon  dioxide)  of  the  air  which  is  the  destructive  agent 
is  shown  by  subjecting  the  plants  to  air  freed  of  carbon  dioxide, 
when  they  are  killed  by  light  as  before. 

The  most  important  results  following  from  the  conclusions 
of  this  sub-section  are  :  a  minimum  vital  limit  of  light  action 
exists  only  in  the  case  of 
those  organisms  (chloro- 
phyllaceous  plants)  which 
depend  upon  light  for  as- 
similation ;  a  maximum 
limit  is  found  among  the 
most  diverse  organisms, 
those  with  chlorophyll 
and  those  without.  The 
rays  which  have  the  more 
rapid  vibrations  are  the 
more  active.  They  pro- 
duce chemical  changes  to 
which  death  is  primarily 
clue. 

3.  Effect  of  Light  upon 
the  Movement  of  Proto- 
plasm.—  Under  this  head 
we  shall  consider  only 
those  protoplasmic  move- 
ments which  may  not  be 
grouped  under  Locomo- 
tion, and  shall  discuss 
three  classes  of  cases : 
(a)  effect  of  low  intensity  of  light  upon  movement ;  (5)  effect 
of  high  intensity  of  light  upon  movement ;  and  (c?)  effect  of 
change  of  intensity  on  contraction. 

a.  Effect  of  Low  Intensity  of  Light  on  Movement — Dark-rigor. 
—  We  have  already  seen  that  chlorophyllaceous  plants  must 
eventually  die  if  kept  in  the  dark.  Some  time  before  death 
occurs  the  plants  go  into  a  condition  of  immobility,  which  may 
be  called  dark-rigor,  since  return  of  light  brings  a  return  of 
movements.  Dark-rigor  is  very  marked  in  the  sensitive  plant. 


FIG.  49.  —  Piece  of  a  sprout  of  Nitella  mucronata 
which  was  subjected  in  a  gas  chamber  to  a 
green  light  in  three  successive  experiments 
A,  B,  C.  In  experiment  A  the  insolation 
lasted  2  to  3  minutes,  the  gas  chamber  be- 
ing filled  with  atmospheric  air.  In  experi- 
ment B  the  insolation  lasted  20  minutes  in 
the  presence  of  hydrogen.  In  experiment  C 
the  insolation  occurred  again  in  the  presence 
of  atmospheric  air  and  lasted  5  to  6  minutes. 
(From  PRIXGSHEIM,  '81.) 


176  LIGHT  AND   PROTOPLASM  [Cn.  VII 

If  this  plant  is  kept  for  several  days  in  darkness,  the  usual 
response  to  touch  does  not  occur.  From  some  observations  of 
.BERT  ('70,  p.  338),  it  appears  that  it  is  the  absence  of  the 
blue-violet  and  orange-red  rays  which  brings  about  this  dark- 
rigor  ;  for  it  occurs  nearly  as  rapidly  in  green  light  as  in  the 
dark.  In  these  cases  the  absence  of  movement  in  the  dark 
might  seem  to  be  the  result  of  diminished  assimilation. 

But  dark-rigor  occurs  under  conditions  which  destroy  the 
general  validity  of  this  conclusion  ;  for  example,  in  the  reddish- 
purple  bacteria  *  whose  reactions  have  been  studied  chiefly  by 
ENGELMANN  ('83  and  '88).  It  appears  that  in  these  organisms 
light  is  essential  to  movement ;  for,  after  having  been  kept 
over  night  in  the  dark,  they  are  found  in  the  morning  at  first 
motionless  ;  only  later,  after  5  to  10  minutes  of  illumination, 
do  they  awaken  to  activity.  If  now,  after  keeping  for  a  time 
in  the  light,  the  organisms  are  brought  again  into  the  dark, 
their  movements  gradually  diminish  until,  in  a  few  hours,  they 
have  ceased.  We  have  seen  above  (p.  51)  that  oxygen  is  nec- 
essary to  movement,  and  we  know  that  many  plants  excrete 
oxygen  in  the  light.  We  might  expect  that  the  quiescence  of 
these  organisms  in  the  dark  is  a  consequence  of  their  failure  to 
produce  the  oxygen  necessary  to  locomotion,  and  indeed  they 
do  produce  in  the  light  a  slight  quantity  of  oxygen,  by  virtue 
of  their  chromophyll  (bacterio-purpurin,  LANKESTER).  But 
that  it  is  not  merely  oxygen  which  induces  movement  is  shown 
by  the  fact  that  when  an  abundant  oxygen  supply  is  artificially 
furnished,  no  movement  occurs  in  the  dark.  Thus  light,  in  the 
presence  of  oxygen,  is  essential  to  movement ;  it  seems  to  be 
necessary  to  the  irritable  condition  upon  which  locomotion 
depends.  This  irritable  state  of  the  protoplasm  conditioned 
upon  a  certain  intensity  of  light  ENGELMANN  calls  phototonus.-\ 

The  analysis  of  this  matter  has  been  carried  further.  It  has 
been  found  that  a  perceptible  time  (latent  period)  elapses 

*  This  term  includes  bacteria  known  as  Bacterium  photometricum,  Bacterium 
roseopersicinum,  rubescens,  etc.,  Monas  okeni,  Spirillum  violaceum,  and  by  other 
names. 

t  The  term  was  applied  to  this  phenomenon  by  ENGELMANN  on  account  of  its 
resemblance  to  that  already  described  for  the  higher  plants,  and  to  which  SACHS 
had  previously  given  this  name. 


EFFECT  UPOX  GENERAL  FUXCTIOXS 


177 


between  the  illumination  of  the  organism  and  the  occurrence 
of  movement.  Also,  the  ultra-red  rays  produce  most  rapid 
locomotion,  next  the  orange-yellow,  and  weakest  the  violet-blue 
and  violet-red.  Spectrum  analysis  shows  that  the  most  active 
rays  are  the  ones  absorbed  by  the  chromophyll  (Fig.  50). 

This  phenomenon  of  phototonus  is  not  confined  to  the  purple 
bacteria.  Thus,  FAMIXTZIN  ('67,  pp.  29-31)  has  shown  that 
the  movements  of  the  closely  related  Oscillaria  are  dimin- 
ished in  the  dark.  SOROKIN  ('78)  found  that  protoplasmic 
streaming  in  the  plasmodium  of  Dictydium  ceases  at  night, 
being  awakened  to  movement  by  the  light.  Finally,  VER- 


a   B    C 


FIG.  50.  —  a.  Spectrum  of  the  chromophyll  of  bacterio-purpurin,  showing  absorption 
bands  at  A  =  0.59  ^  and  A  =  0.53  /n.  An  (invisible)  absorption  band  has  been  deter- 
mined by  means  of  the  bolometer  at  \  =  0.85  M.  6.  The  bacteria  are  seen  aggre- 
gated chiefly  in  the  regions  of  the  absorption  bands.  The  accumulation  of  bacteria 
in  these  regions  of  absorbed  energy  seems  due  to  the  fact  that  the  moving  bacteria 
cannot  pass  from  a  region  of  high  energy  to  one  of  low  without  a  violent  stimulus 
which  impels  them  back  again.  (From  ENGELMANN,  '83*.) 


X  ('89,  Nachschrift,  and  '95,  p.  393)  finds  that,  in  the 
dark,  the  ciliate  Pleuronema  chrysalis  rests  quietly  in  the 
water,  only  occasionally  making  its  peculiar  spring.  But 
when  diffuse  daylight  is  focussed  upon  it,  for  instance  by  the 
mirror  of  a.  microscope,  it  springs  rapidly  by  the  movement  of 
its  long  cilia  ;  and  this  movement  is  often  repeated,  so  long  as 
light  continues  to  fall.  The  movement  is  produced  by  blue  or 
violet  rays  ;  red  rays  have  little  or  no  effect.  A  latent  period 
of  from  1  to  3  seconds  elapses  before  the  response  occurs. 

These  cases  serve  to  show  that  light,  in  the  presence  of  other 
suitable  conditions,  is,  both  for  some  chlorophyllaceous  organ- 
isms and  plant  tissues  and  for  some  organisms  destitute  of 


178  LIGHT   AND   PROTOPLASM  [Cn.  VII 

chlorophyll,  nearly  or  quite  essential  to  movement.     Phototo- 
mis  is  a  convenient  name  for  the  condition  induced  by  light. 

b.  Effect  of  High  Intensity  of  Light  on  Movement  —  Light- 
rigor. —  We  have  just  seen  that  in  some  organisms  the  most 
vigorous  movements  occur  at  an  optimum  intensity  of  light, 
which  produces  phototonus.     At  a  lower  intensity  there  is  no 
movement.     It  appears,  furthermore,  that  there  is  for  many  or- 
ganisms a  maximum  intensity  of  light,  below  that  which  produces 
death  (ultramaximum),  which  causes  a  cessation  of  movement 
that  may  be  called  light-rigor.     This  condition  is  distinguished 
from  that  of  death  by  the  fact   that  diminished  light  brings 
return  of  activity.     ENGELMANN  ('82,  p.  109)  observed  this 
condition  in  his  Bacterium  photometricum,  and  remarks  that 
it  is   common   to  all   bacteria.     Similar   light-rigor   has  been 
observed   in   green  plants   also.     PRINGSHEIM   ('81,  p.   516) 
found  that  when,  in  the  presence  of  oxygen,  strong  sunlight 
was   let   fall   upon   Nitella,    the   movements    ceased   after    1J 
minutes.     If  the  insolation  was  now  interrupted,  normal  move- 
ments were  resumed. 

Summing  up  the  effects  of  varied  intensities  of  light,  it 
appears  that  for  many  organisms  there  is  an  optimum,  which 
produces  a  condition  of  phototonus,  in  which  the  organism 
moves  and  responds  regularly  to  stimuli.  As  the  light  inten- 
sity falls  below,  or  rises  above  this  optimum,  the  activity  of 
movement  diminishes,  ceasing  at  certain  points  in  the  condi- 
tions of  dark-rigor  and  light-rigor.  Beyond  each  of  these 
points,  again,  is  the  point  of  death. 

c.  Contraction  produced  by  Change  in  Intensity  of  Illumina- 
tion. —  We  here  consider  a  number  of  cases  not  closely  related 
except  in  this,  that  quick  movements  are  produced  after  stimu- 
lation by  change  in  the  intensity  of  the  light.     The  cases  are 
found  both  among  Protista  and  Metazoa. 

Among  the  sulphur-bacteria  ENGELMANN  ('88,  p.  665  ;  88a) 
has  noticed  that  a  sudden  diminution  in  the  intensity  of  the 
light,  produced  by  shading  the  mirror  of  the  microscope,  is 
followed  by  a  spring  backwards,  often  to  the  distance  of  10 
to  20  times  the  organism's  length.  This  reaction  ENGEL- 
MANN  has  called  "  Schreckbewegung."  When  the  light  is  sud- 
denly increased,  a  forward  movement  takes  place,  but  this  is 


§3]  EFFECT  UPON   GENERAL  FUNCTIONS  179 

less  marked.  Among  the  Myxomycetes,  ENGELMAXX  ('79) 
has  found  that  the  amo3boid  Pelomyxa,  when  suddenly  sub- 
jected to  a  strong  light,  contracts  into  a  spherical  mass.  X 
Sudden  darkening  or  gradual  illumination  produces  no  such 
contraction.  Among  swarm-spores,  STRASBURGER  ('78,  pp.  575, 
576)  has  noticed  that  a  sudden  diminution  of  the  light  puts 
the  quiet  Hsematococcus  spores  again  in  motion,  and  makes  the 
Botrydium  spores  start  as  though  disturbed.  Such  violent 
movements  of  the  protoplasm  indicate  that  a  very  considerable 
chemical  change  has  taken  place  in  it. 

Passing,  next,  to  the  Metazoa,  we  find  that  certain  smooth 
muscle  fibres  are  made  to  contract  by  the  direct  action  of  light ; 
thus,  STEIXACH  ('92)  has  offered  most  convincing  evidence 
that  the  contraction  of  the  iris,  in  the  lower  vertebrates  at 
least,  may  occur  as  a  direct  reaction  to  illumination,  even  when 
the  eyeball  is  cut  out,  and  the  iris,  indeed,  separated  from 
connection  with  the  ciliary  part  of  the  eye. 

Some  of  the  higher  animals  react  strikingly  like  EXGEL- 
MAXN'S  bacteria.  Thus,  LOEB  ('93,  p.  103)  found  that  Serpula 
uncinata  retracts  into  its  tube  when  the  hand  is  passed  between 
it  and  the  light ;  but  sudden  increase  of  illumination  has  no 
effect.  NAGEL  ('96,  p.  76)  finds  the  same  thing  in  Spirographis, 
and  ANDREWS  ('91,  pp.  285,  296)  has  observed  the  same  phe- 
nomenon in  the  eyeless  Hydroides  dianthus.  In  these  cases 
the  branchiye  seem  to  be  the  sensitive  organs.  Adult  barnacles 
show  a  similar  sensitiveness  to  light;  for  POUCHET  ('72,  p.  Ill) 
found  that  momentary  cutting  off  of  the  light,  as  by  the  shadow 
of  the  hand,  caused  arrest,  for  several  seconds,  of  the  rhythmic 
movements  of  protrusion  of  the  appendages  from  the  shell.  In 
this  case,  the  sensitive  region  has  not  been  located.  Some 
lamellibranchs  (XAGEL,  '96,  p.  50)  react  similarly  to  increased 
light.  These  are  examples  of  a  phenomenon  which  we  shall 
meet  with  again  in  considering  growth.  They  serve  to  show 
that  there  is  a  wide-spread  irritability  of  protoplasm  to  changes 
in  intensity  of  light. 

Let  us  now  review  the  conclusions  of  this  section.  Light  — 
especially  the  thermic  rays  —  is  essential  to  the  decomposi- 
tion of  carbon  dioxide  by  chlorophyllaceous  plants.  The  only 
effective  rays  are  those  absorbed  by  the  chlorophyll.  The  rate 


180  LIGHT  AND  PROTOPLASM  [Cn.  VII 

of  assimilation  is  increased  by  increased  intensity  of  light.  The 
chemical  rays  act  to  increase  metabolic  changes,  and  the  output 
of  carbon  dioxide.  As  these  rays  become  more  intense,  the 
metabolic  changes  go  on  with  abnormal  rapidity,  until,  finally, 
death  ensues;  thus,  intense  light  is  fatal  to  many,  perhaps  to 
all,  organisms.  Absence  of  light,  however,  is  injurious  only  as 
preventing  assimilation  in  chlorophyllaceous  organisms ;  but 
these  supply  the  food  for  other  organisms,  so  that  continued 
darkness  in  any  environment  must  likewise  be  eventually  fatal 
to  all  life.  All  organisms,  before  succumbing  to  darkness  or 
to  light,  enter  into  a  condition  of  rigor,  from  which  they  may 
return  to  activity  if  favorable  conditions  are  restored.  Sudden 
change  of  intensity  often  produces  violent  protoplasmic  changes, 
awakening  quiescent  organisms  to  activity,  or  causing,  in  the 
higher  organisms,  violent  contractions. 

All  of  these  effects  of  light,  whether  produced  by  the  thermic 
or  chemic  rays,  probably  give  rise  to  great  chemical  changes 
by  which  disturbances  of  metabolism,  and  eventually  death, 
may  be  produced.  Not  all  organisms  find  light  immediately 
necessary  to  their  existence;  but  very  powerful  light,  long 
continued,  proves  fatal  to  most  protoplasm. 


§  4.     CONTROL  OF  THE  DIRECTION  OF  LOCOMOTION  BY 
LIGHT  —  PHOTOTAXIS  AND  PHOTOPATHY  * 

In  this  section  we  shall  (1)  distinguish  between  false  and 
true  phototaxis ;  (2)  consider  the  observed  cases  of  phototaxis 
among  Protista,  the  parts  of  higher  organisms,  and  the  Metazoa 
as  entire  organisms ;  and  (3)  discuss  the  general  laws  of  photo- 
taxis  and  photopathy. 

*  In  this  section  we  shall  deal  with  two  sets  of  phenomena  which  very  likely 
are  different,  but  which,  in  our  ignorance,  we  cannot  always  distinguish.  The 
first  includes  that  active  migration  of  organisms  whose  direction  is  determined 
by  that  of  the  rays  of  light.  This  is  phototaxis.  The  second  includes  the 
wandering  of  organisms  into  a  more  or  less  intensely  illuminated  region,  the 
direction  of  locomotion  being  determined  by  a  difference  in  intensity  of  illumina- 
tion of  the  two  poles  of  the  organism.  This  is  photopathy.  According  as  the 
migration  is  towards  or  from  the  source  of  light,  we  can  distinguish  positive  (  +  ) 
and  negative  ( — )  phototaxis.  According  as  the  migration  is  towards  or  from 
the  more  intensely  illuminated  area,  we  can  distinguish  positive  (  +  )  and  negative 


4]  PHOTOTAXIS  AXD  PHOTOPATHY  181 


OK 

re] 


1.  False  and  True  Phototaxis.  — It  must  certainly  be  a  very 
old  observation  that  when  small  organisms  are  placed  in  a 
ssel  in  front  of  a  window,  they  are  soon  found  arranged  with 
ference  to  the  window ;  some  lying  on  the  nearer  side,  some 
on  the  further  side,  and  others  swimming  indifferently  back 
and  forth  through  the  vessel.  The  conclusion  is  near  at  hand 
that  this  arrangement  of  the  organisms  is  determined  by  the 
light.  This  conclusion  is,  however,  not  necessarily  correct. 
Thus,  SACHS  ('76)  showed  that,  under  certain  conditions, 
wholly  passive  substances  —  oil  drops,  in  a  mixture  of  water 
and  alcohol  —  might  exhibit  a  similar  aggregation  towards  the 
window  or  away  from  it.  These  conditions  are  that  the  vessel 
should  be  cooler  next  the  window.  Then,  on  tlie  cooler  side, 
there  will  be  a  descending  current ;  on  the  warmer  side,  an 
ascending  current ;  on  the  surface,  a  current  towards  the  win- 


a 

FIG.  51.  — Vertical  section  through  a  dish  showing  distribution  in  water  of  passively 
suspended  bodies,  as  a  result  of  difference  of  temperature  at  the  two  sides  of  the 
vessel.  .1,  warmer  side ;  B,  cooler  side.  Arrows  show  the  direction  of  movement 
of  currents  in  the  water.  The  objects  lighter  than  water  are  grouped  at  b ;  those 
heavier  than  water,  at  a. 

dow ;  and  on  the  bottom,  a  current  from  the  window.  If 
the  passive  bodies  are  such  as  float,  they  will  thus  be  carried 
towards  the  window,  and  will  exhibit  a  false  phototaxis  (in 
the  positive  sense);  if,  on  the  contrary,  they  tend  to  sink,  they 
will  be  carried  from  the  window,  and  show  false  negative  pho- 
totaxis. Xow  this  appearance,  due  to  passive  transportation 
by  currents,  may  likewise,  under  the  given  conditions,  be 
exhibited  by  organisms  —  but  the  phenomenon  is  not  due  to 
light  (Fig.  51). 

There  is  at  least  one  other  kind  of  pseudophototaxis.     This 

(— )  photopathy  ;  and  correspondingly  we  can  in  this  second  case  speak  of  the 
organisms  themselves  as  photophil  or  photophob.  In  this  nomenclature  I  follow 
GRABER.  STRASBURGER  used  photometry  for  what  I  here  call  photopathy,  but 
OLTMAXNS  ('92,  p.  206)  has  employed  photometry  to  indicate  the  capacity  of 
organisms  to  perceive  different  degrees  of  intensity  of  light.  So,  perhaps,  the 
terminology  here  employed  may  lead  to  the  least  confusion. 


182  LIGHT   AND   PROTOPLASM  [Cn.  VII 

may  occur  when  there  are  in  the  vessel  chlorophyllaceous 
organisms  producing  oxygen  in  the  sunlight.  The  oxygen, 
more  abundantly  formed  on  the  sunny  side  of  the  vessel,  becomes, 
then,  a  means  of  attraction  to  other  (chemotactic)  organisms, 
whose  position  seems  thus  to  be  determined  directly  by  relative 
brightness. 

A  good  example  of  this  kind  of  pseudophototaxis  is  described  by  ENGEL- 
MANN  ('81a):  He  found  that  the  Schizomycetes  in  a  certain  drop  of  water, 
partially  illuminated,  were  aggregated  toward  the  illuminated  side.  Exami- 
nation revealed  the  presence  of  a  chlorophyllaceous  schizomycete  —  Bacte- 
rium chlorinum  —  in  the  drop,  and  the  apparent  phototactic  appearances  were 
easily  accounted  for  as  follows  :  Under  the  influence  of  light  the  Bacterium 
chlorinum  secreted  oxygen,  and  this  acted  chemotactically  to  attract  the 
bacteria,  which  thus  moved,  at  the  same  time,  towards  the  illuminated 
area.  That  it  was  the  oxygen  produced  in  the  sunlight  rather  than  the 
light  itself  which  attracted,  was  evinced  by  the  fact  that,  when  the  supply 
of  oxygen  is  abundant  in  all  parts  of  the  drop,  or  if  the  Bacterium  chlorinum 
is  removed,  no  aggregation  takes  place  at  the  bright  point. 

2.  Distribution  of  Phototaxis  and  Photopathy.  —  a.  Protista. 
—  We  now  come  to  the  consideration  of  the  cases  of  true  pho- 
totaxis  and  photopathy,  and  shall  first  discuss  the  distribution 
of  the  phenomenon  in  the  different  groups  of  Protista.  Of  the 
Protista  we  may  take  up  first  the  chlorophyllaceous  forms. 

Flagellata  and  Swarm-Spores.  —  In  no  other  group  does 
phototaxis  show  itself  more  clearly  than  in  this.  The  earliest 
studies  were  made  here,  but  despite  the  ease  of  gaining  results 
they  were  mostly  fragmentary  and  uncritical.  A  simple  ex- 
periment of  NAGELI  ('60)  had,  indeed,  showed  conclusively 
that  swarm-spores  are  responsive  to  light.  A  glass  tube  three 
feet  long  and  held  vertically  was  filled  with  alga- water.  When 
the  upper  end  of  the  tube  was  enveloped  by  black  paper  the 
organisms  moved  to  the  lower  end,  and  conversely.  A  diffi- 
culty was  encountered,  however,  in  the  fact  that  when  zoospores 
were  placed  in  a  plate  by  a  window,  the  organisms  gathered 
at  the  edge  next  the  window,  which,  since  the  edge  of  the  plate 
threw  a  shadow  there,  was  the  darkest  part  of  the  surface. ,  In 
consequence  some  authors  had  concluded  that  swarm-spores 
shun  the  light ;  whereas  COHN  asserted,  all  too  briefly,  that 
they  move  in  the  direction  of  the  rays  and  toward  the  source 
of  light.  Finally,  FAMINTZIN  ('67)  had  discovered  that  swarm- 


§4]  PHOTOTAXIS   AND   PHOTOPATHY  183 

spores  which  moved  towards  a  light  of  a  certain  intensity  would 
move  from  light  of  a  certain  greater  intensity.  That  was  the 
condition  of  knowledge  on  this  subject  when  STRASBURGER'S 
('78)  epoch-making  paper  appeared. 

STRASBURGER  worked  with  swarm-spores  of  various  species 
of  algoe,  and  with  the  flagellate  Chilomonas  and  Euglena.  He 
observed  again  the  phenomenon  that  the  sense  ( 4-  or  — )  of 
response  depends  upon  the  intensity  of  the  light.  He  also 
showed  that  the  rate  of  movement  is  quicker  in  stronger  light 
on  account  of  the  fact  that  the  path  taken  by  the  organism  is 
straighter  ;  and  (p.  586)  that  phototaxis  is  the  result  of  the 
organism  putting  its  long  axis  in  the  axis  of  the  inf ailing  rays. 
STRASBURGER  found  also  that,  in  general,  the  smaller  species 
of  swarm-spores  and  the  smaller  individuals  are  more  respon- 
sive than  the  larger  ones. 

Later  studies  have  extended  our  knowledge  of  the  distri- 
bution of  phototaxis  in  this  group.  Swarm-spores  have  been 
studied  by  STAHL  (78,  '80)  ;  Euglena,  by  ENGELMANN  ('82% 
p.  396)  ;  and  Volvox,  by  CIENKOWSKI  ('56),  VERWORN 
('89,  p.  45),  and  OLTMANNS  ('92).  Especially  interesting 
is  the  fact  that  colorless  swarm-spores,  like  those  of  Chytri- 
diurn,  which  are  parasitic  upon  chlorophyllaceous  forms,  respond 
like  the  green  organisms.  (STRASBURGER,  '78,  p.  568.) 

Desmids,  especially  Closterium,  have  been  experimented  with 
by  STAHL  ('78  and  '79),  KLEBS  ('85),  and  ADERHOLD  ('88). 
All  are  markedly  phototactic  in  moderate,  diffuse  daylight. 
This  phototaxis  is  the  more  striking  since  the  method  of  loco- 
motion of  these  forms  is  peculiar.  The  crescentic  Closterium 
moniliferum,  for  example,  stands  inclined  and  glides  along,  one 
extremity  touching  the  substratum,  the  free  extremity  in  ad- 
vance. The  gliding  seems  to  result  from  the  secretion  of  a 
stream  of  mucus  along  the  substratum.  Now  STAHL  believed 
that  the  angle  of  inclination  of  the  Closterium  is  dependent 
upon  the  direction  of  the  iiifalling  rays  of  light,  being  parallel 
thereto.  This  relation  has  been  denied  by  KLEBS,  but  ADER- 
HOLD, by  varying  the  direction  of  the  infalling  rays,  has  shown 
that  the  azimuthal  position  is  determined  by  light.  Under 
certain  conditions  Closterium  moniliferum  moves  by  a  sort  of 
head-over-heels  motion,  since  the  free  end  bends  down  to  the 


184  LIGHT   AND   PROTOPLASM  [Cn.  VII 

substratum  and  becomes  attached,  and  the  former  attached  end 
becomes  free.  STAHL  explains  this  on  the  ground  that  the 
ends  of  Closterium  periodically  exchange  their  tendency  to 
point  towards  the  light.  The  appearances  just  described  are 
found  in  diffuse  daylight.  In  stronger  light  the  azimuthal 
position  is  90°  from  the  infalling  light.  If  direct  sunlight 
falls  upon  desmids,  they  move  from  the  light  (negative  pho- 
totaxis). 

Diatoms  have  been  studied  by  STAHL  ('80)  and  VERWORN 
('89,  p.  47).  Locomotion  is  effected  in  these  organisms  as  in 
desmids  by  the  secretion  of  mucous  threads.  The  movement 
towards  diffuse  daylight  (Navicula,  Stauroneis)  takes  place 
slowly,  but  it  often  affects  nearly  all  the  individuals.  The 
long  axis  does  not  seem  to  be  clearly  oriented  in  the  direction 
of  the  infalling  rays,  which  may  be  partly  accounted  for  by 
the  normal  zigzag  method  of  locomotion.  Under  strong  sun- 
light diatoms  appear  negatively  phototactic.  Occasionally  a 
culture  will  be  found  whose  individuals  are  separated  into  two 
groups  —  one  next  the  positive  side,  the  other  next  the  nega- 
tive side  of  the  vessel. 

Oscillaria.  —  VERWORN  ('89,  p.  50)  has  made  experiments 
on  the  reaction  of  these  organisms,  whose  method  of  locomotion 
is  probably  similar  to  that  of  desmids.  They  are  markedly 
positively  phototactic  from  half  darkness  to  direct  sunlight ; 
only  in  intense  sunlight  do  they  fail  to  accumulate  at  the  posi- 
tive end  of  the  vessel.  The  aggregation  at  the  positive  pole 
takes  place  by  the  threads  assuming  a  direction  parallel  to  the 
rays  of  light  and  creeping  forward  thus,  side  by  side.  VER- 
WORN  states  that  after  all  have  attained  the  +  edge,  rotation 
of  the  slide  or  vessel  through  180°  does  not  cause  a  prompt 
transfer  of  all  individuals  towards  the  light  side  —  at  least 
during  the  time  of  his  observation  only  a  few  had  crawled 
towards  the  light  in  its  new  position.  According  to  WINO- 
GRADSKY  ('87),  Beggiatoa  is  generally  negatively  phototactic. 

Myxomycetes.  —  In  its  amosboid  form  and  when  subjected  to 
strong  sunlight  ^Ethalium  septicum  retreats  into  the  substratum, 
but  while  in  the  dark  it  comes  to  the  surface  (HOFMEISTER,  '67, 
p.  625  ;  STRASBURGER,  '78,  p.  620).  Also,  when  the  plasmo- 
dium  is  partially  illuminated,  the  protoplasm  tends  to  flow  from 


PHOTOTAXIS  AXD  PHOTOPATHY 


185 


the  illuminated  region.     (BARAXETZKI,  '76,  p.  328,  and  STAHL, 
'84,  p.  167.) 

BARAXETZKI  proceeded  as  follows:  a  glass  plate  was  placed  in  a  saucer  so 
that  its  surface  was  2  or  3  mm.  below  the  rim.  The  plate  was  covered  by 
filter  paper  which  extended 
over  the  rim  and  here  dipped 
into  water,  by  which  means 
it  was  kept  moist.  Over  the 
saucer  was  '  laid  an  opaque 
cover,  blackened  below  and 
provided  with  a  narrow  slit. 
The  plasmodium  was  placed 
on  the  filter  paper  and  diffuse 
daylight  was  thrown  upon  the 
slit  by  means  of  a  plane  mir- 
ror. In  less  than  half  an  hour 
the  illuminated  threads  of  the 
plasmodium  had  become  very 
thin,  owing  to  the  retreat  of  the 
protoplasm  from  under  the  slit 
to  the  darker  region  (Fig.  52). 

Rhizopoda. — Although, 
as  we  have  seen,  Pelo- 
myxa  is  irritated  by  a 
sudden  illumination,  a 
phototactic  or  photo- 
pathic  response  has  not 
hitherto  been  certainly 
observed  in  this  group.  VERWORX  ('89,  pp.  40,  41),  indeed, 
experimented,  but  with  negative  results,  upon  Amoeba  limax, 
Amoeba  princeps,  Actinosphserium,  and  Actinophrys.  Only 
in  Polystomella  crispa  did  he  notice  a  slow  wandering 
towards  the  source  of  light ;  but  he  was  uncertain  whether 
this  was  due  to  light. 

VERWORX'S  method  was  not  well  devised,  however,  for  bringing  out 
phototactic  response.  The  Protista  were  placed  on  the  slide,  and,  after  cut- 
ting out  heat  rays  by  means  of  a  plate  of  ice,  were  subjected  to  the  light  or 
to  the  EXGELMANN  microspectrum,  and  illuminated  at  different  intensities 
either  over  the  whole  body  or  over  only  a  part.  All  disturbing  influences, 
he  says,  were  as  far  as  possible  eliminated :  gravity,  by  an  exact  horizontal 
position  of  the  microscope  on  a  table  with  three  screw-feet ;  the  action  of 
the  edge  of  the  drop,  by  using  a  very  broad  drop ;  and,  finally,  the  laterally 


FIG.  52.  —  Plasmodium  of  ^Ethalium  septicum, 
after  having  been  kept  in  the  dark  for  some 
time  and  then  illuminated,  for  half  an  hour, 
over  a  cross-shaped  area,  only.  The  illumi- 
nated area  is  on  the  upper  part  of  the  figure. 
The  protoplasm  has  retracted  from  it,  leaving 
a  partially  clear  region  in  the  form  of  a  cross. 
(From  BARAXETZKI,  '75.) 


186  LIGHT   AND   PROTOPLASM  [Cn.  VII 

impinging  rays  of  light,  by  means  of  a  black  cardboard  box  placed  over  the  slide. 
Thus  it  is  clear  that  all  of  his  light  fell  upon  the  organism  in  perpendicular 
rays  from  below.  This  method  of  experimentation  would  clearly  not  show 
whether  Amoeba  is  phototactic  or  not. 

I  have  experimented  with  Amoeba  proteus,  using  methods 
resembling  VERWORN'S,  and  likewise  dissimilar  ones,  and  have 
reached  new  results.  In  the  first  place,  I  have  proceeded  some- 
what after  the  fashion  of  VERWORN  to  determine  whether  the 
amoeba  in  a  field  illuminated  from  below,  and  separated  by  a 
sharp  line  into  a  light  and  dark  half,  showed  any  change  of 
movement  in  passing  from  dark  to  light  or  from  light  to  dark ; 
also,  whether  an  amoeba  moving  in  a  uniformly  illuminated 
field  changed  its  direction  when  half  of  its  body  was  dark- 
ened. Nearly  all  such  experiments  were  negative.  No  effect 
resulting  from  the  change  from  light  to  dark  or  the  reverse 
could  be  detected.  Thus  far  my  results  agreed  with  VER- 
WORN'S. 

In  a  second  set  of  experiments,  I  proceeded  differently. 
Usually  one  amoeba  was  isolated  by  means  of  a  capillary  tube. 
It  was  then  introduced,  with  a  drop  of  clear  water,  between 
two  slips  of  glass,  each  about  25  by  50  mm.,  which  were  kept 
2  mm.  apart,  and  at  the  same  time  cemented  together,  by  glass 
strips  of  equal  thickness  placed  near  the  ends.  By  this  means  a 
broad  field  for  movement  with  uniformity  of  conditions  of  con- 
tact was  ensured.  The  whole  space  between  the  two  glass  plates 
being  now  filled  with  clear  water,  the  entire  apparatus  was  sub- 
merged in  a  vessel  which  contained  water  about  2  cm.  deep, 
and  which  was  slightly  smaller  than  the  stage  of  the  micro- 
scope. Finally,  the  entire  stage,  but  not  the  substage  optical 
apparatus,  was  kept  in  the  dark  by  means  of  a  cone  made  of 
several  thicknesses  of  dense  black  cloth  fastened  by  a  slip-noose 
to  the  objective,  and  folded  below  the  stage  so  as  completely  to 
exclude  all  extraneous  lateral  light.  Light  from  the  mirror 
was  cut  off  by  an  interposed  card.  Through  a  slit  in  the  cloth 
on  the  side  next  the  window,  —  a  west  window,  —  a  beam  of 
direct  sunlight,  or  of  reflected  light  from  the  morning  sky,  was 
admitted  to  the  amoeba.  The  plates  of  glass  being  as  nearly  as 
possible  horizontal  and  occasionally  rotated,  the  directive  action 
of  gravity  was  eliminated.  Since,  so  far  as  could  be  seen  with 


§  4]  PHOTOTAXIS   AND   PHOTOPATHY  187 

the  microscope,  no  local  sources  of  food  or  oxygen  occurred  in 
the  water  between  the  plates  of  glass,  chernotactic  influences 
were  uniformly  distributed.  From  the  conditions  of  the  ex- 
periment already  described,  a  difference  in  temperature  or  of 
illumination  at  the  two  poles  of  the  amoeba  is  scarcely  conceiv- 
able. The  rays  of  radiant  energy  were  the  only  directing  agent. 
Under  these  conditions  the  amoeba  nearly  uniformly  showed 
itself  negatively  phototactic  to  light  of  an  intensity  varying 
from  strong  diffuse  light  to  direct  sunlight.  The  absence  of 
uniformity  is  to  be  ascribed  to  the  accidental  presence  of  some 
disturbing  agent.  The  movements  made  by  the  amoeba  were 
represented  graphically  by  making  at  intervals  a  camera  drawing 
of  its  outline.  Two  such  graphic  representations  are  repro- 
duced in  Figs.  53  and  54.  It  must  be  said  that  it  is  difficult  to 
get  so  extended  a  series  of  changes  in  light  as  is  shown  in  Fig. 
54,  for  the  phenomenon  of  acclimatization  comes  in  and  the 
responses  become  irregular.  But,  despite  such  irregularities, 
my  studies  lead  me  unhesitatingly  to  conclude  that  Amoeba, 
although  not  at  all  photopathic,  is  strongly  phototactic.  This 
result  is  important,  for,  since  Amoeba  is  responsive  to  light,  it 
may  very  well  be  that  such  responsiveness  is  a  general  property 
of  protoplasm. 

Ciliata.  —  A  double  action  of  light  must  be  here  taken  into 
account.  EXGELMAXX  ('82a,  pp.  391-395)  states  that  those 
Ciliata  which  contain  chlorophyll  (algse)  —  e.g.  Paramecium 
bursaria,  Stentor  viridis,  Bursaria  —  move  towards  the  light, 
but  only  when  the  oxygen  tension  in  the  water  is  low.  Also 
when  the  water  drop  is  illuminated  by  a  microspectrum,  instead 
of  white  light  the  organisms  aggregate  towards  the  red  end. 
Here  are  the  rays  by  which  most  oxygen  is  produced  from  the 
chlorophyll,  since  assimilation  takes  place  fastest  here.  When 
the  organisms  are  placed  in  excessively  oxidized  water  they 
move  from  the  light.  The  conclusions  to  which  EXGELMAKN 
arrived  from  these  and  other  facts  were  that  these  species  have 
a  very  delicate  sensitiveness  to  variations  in  oxygen  tension,  and 
that  it  is  through  this  sensitiveness  that  light  influences  move- 
ment. Accordingly,  it  would  seem  that  the  apparent  photo- 
taxis  is  truly  a  case  of  chemotaxis  ;  but  this  conclusion  requires 
better  evidence. 


188 


LIGHT  AXD  PROTOPLASM 


[Cn.  VII 


11:22 


11:18 


(2).   14:OO  to  14:2O 


ft'" 


11:12 


11:02 


10:55 


ft 


10:44 


I 


13:06 


(3).    14:20  to  14:34 


FIG.  53.  — Camera  drawing,  showing 
the  successive  positions  assumed 
by  an  amoeba  subjected  to  light 
falling  upon  it  from  one  side.  The 
arrow  lies  in  a  horizontal  projec- 
tion of  the  sun's  rays.  The  amoeba 
retreats  from  the  source  of  light. 
The  numbers  to  the  right  of  the 
outlines  of  the  amoeba  give  the 
observed  times  between  10:28  and 
11 :22  A.M.  Magnified  16  diameters. 

FIG.  54.  —  Camera  drawing,  showing 
the  successive  positions  assumed 
by  an  amoeba  retreating  from  the 
light.  The  position  of  the  infalling 
ray  was  successively  changed  from 
(1)  to  (2),  (3),  and  (4).  The  arrow 
labelled  "  First  direction  of  migra- 
tion "  shows  the  direction  of  loco- 
motion of  the  amoeba  before  the 
light  fell  upon  it  at  the  beginning  of 
the  experiment.  The  numbers  indi- 
cate hours  and  minutes.  During  the 
interval  from  13:06  (=1:06)  P.M.  to 
13:57,  the  amoeba  was  not  under  di- 
rect observation,  since  I  was  called 
away.  Magnified  16  diameters. 


Cases  that  can  be  explained  only  on  the  ground  of  the  imme- 
diate effect  of  light  upon  the  direction  of  movement  are  cer- 
tainly rare.  ENTZ  ('88),  indeed,  has  intimated  that  Opalina 
flees  from  light,  but  VERWORN  ('89,  pp.  53-57)  was  not  able 
to  confirm  him  in  this  point.  VERWORN'S  method  was  here, 
as  in  the  case  of  Amoeba,  not  satisfactory.  Instead  of  having 
the  light  fall  from  one  side  only  upon  the  drop  containing  the 
Opalinas,  he  let  the  light  pass  vertically  from  below  through  a 
small  hole,  and  could  observe  no  tendency  to  avoid  the  illu- 


10:34 


,10:28 


13:00 


12:54 


§4]  PHOTOTAXIS   AND   PHOTOPATHY  189 

minated  spot.  The  light  in  this  case  clearly  did  not  act  from 
one  side,  and  the  test  of  phototaxis  can  therefore  hardly  be  said 
to  have  been  critically  made.  Likewise,  even  with  unilateral 
illumination,  VERWORN  was  unable  to  gain  a  phototactic  re- 
sponse with  Stentor  rceselii,  St.  coeruleus,  Carchesium  polypi- 
num,  and  Uroleptus  musculus.  On  the  other  hand,  we  have 
often  noticed  here  in  Cambridge  that  our  Stentor  coeruleus  is 
(rather  indefinitely)  negatively  phototactic  to  diffuse  daylight. 
Thus,  an  individual  swimming  free  in  a  bit  of  glass  tubing 
pointing  horizontally  towards  the  window  only  very  slowly 
wanders  away  from  the  light.  In  conclusion,  then,  we  must 
admit  that  Ciliata  are  not  markedly  phototactic,  but  more 
refined  methods  must  be  used  before  we  can  say  of  any  of 
them  that  they  exhibit  no  trace  of  this  response. 

Let  us  summarize  briefly  the  results  obtained  from  Protista. 
Phototaxis  is  most  marked  among  actively  motile,  chlorophyl- 
laceous  forms.  Many  colorless  forms  are,  however,  also  photo- 
tactic  —  Beggiatoa,  Amoeba,  plasmodia  of  Myxomycetes,  and 
swarm-spores  of  Chytridium.  The  phenomenon  is  thus  wide- 
spread, if  it  is  not  universal. 

b.    Cells  and  Cell-organs.  —  Under  this  head  will  be  consid-   r* 
ered,   (a)   the   rearrangement   of   chlorophyll   corpuscles,   (/3) 
the  rearrangement  of   pigment   in   animal  cells,  and  (7)  the 
migration  of  pigment  cells  in  the  metazoan  body. 

a.  That  the  chlorophyll  bodies  of  the  higher  plants  change 
their  position  in  the  cell  according  to  the  intensity  of  the  light 
to  which  they  are  subjected  has  been  made  known  chiefly 
through  the  labors  of  FAMIXTZIN  ('67),  BORODIN  ('69), 
FRANK  ('72),  STAHL  ('80),  and  MOORE  ('87).  If  one  fastens 
a  strip  of  black  paper  upon  a  leaf  on  which  the  sun's  rays  are 
falling,  one  will  find,  upon  removing  the  paper  after  a  time, 
that  the  darkened  part  is  dark  green  whilst  the  brightly  illu- 
minated part  is  considerably  lighter,  so  that  an  image  of  the 
form  of  the  dark  paper  is  produced  upon  the  leaf.  This  image 
is,  however,  only  temporary.  A  few  hours  after  the  removal 
of  the  paper  the  leaf  is  of  a  uniform  green  again.  Sections 
through  a  leaf  thus  affected  show  that  in  the  dark  green 
(shaded)  part  of  the  leaf  the  chlorophyll  lies  on  those  walls 
of  the  cells  which  are  perpendicular  to  the  incoming  rays, 


190 


LIGHT  AND  PROTOPLASM 


[Cn.  VII 


whilst  in  the  light  green  (illuminated)  part  of  the  leaf  the 
chlorophyll  lies  upon  the  walls  parallel  to  the  rays.     When 

the  grains  are  upon  the 
superficial  face  of  the 
cells  they  are  said  to  be 
in  epistrophe;  when  they 
have  turned  away  from 
this  face  they  are  in  apos- 
trophe. This  apostrophic 
position  is  found  under 
two  opposite  conditions 
of  illumination  :  under 
intense  light,  as  we  have 
just  seen  (positive  apos- 
trophe, MOORE),  and  upon 
prolonged  standing  in  the 
dark  (negative  apostro- 
phe). (Fig.  55.) 

It  appears,  then,  that 
epistrophe  occurs  only 
within  certain  limits  of 
light  intensity.  The  in- 
tensities included  between 
these  limits  constitute 
what  MOORE  calls  the 
epistrophic  interval.  The 
epistrophic  interval  varies 
in  position  and  in  extent 

in  different  species.*     It  has  been  found  that  in  the  case  of 
plants  which  normally  live  in  the  bright  sun  the  epistrophic 

*  The  limits  were  determined  by  MOORE,  in  a  roughly  quantitative  way,  by 
means  of  his  photrum,  constructed  as  follows.  A  room  with  a  single  window 
illuminated  by  the  sun  was  chosen  and  12  feet  spaced  off  from  the  window  back 
into  the  darkness.  The  intensity  of  the  light  diminished  of  course  as  one  re- 
treated from  the  window.  Plants  of  various  species  were  allowed  to  stand, 
simultaneously,  at  varying  distances  from  the  window,  and  the  distance  back  at 
which  epistrophe  began  to  appear,  and,  finally,  at  which  negative  apostrophe 
came  in,  were  noted.  Then  a  diagram  ^  the  actual  scale  was  made  (Fig.  56), 
showing  the  position  of  the  points  of  beginning  and  ending  of  epistrophe  (so- 
called  positive  and  negative  critical  points). 


FIG.  55.  —  Cross-section  through  the  leaf  of 
Lemna  trisulca.  A.  Position  of  the  chlo- 
rophyll grains  in  diffuse  daylight  —  epis- 
trophe. -B.  Position  of  the  chlorophyll 
grains  in  intense  light  —  positive  apos- 
trophe. C.  Position  of  the  chlorophyll 
grains  in  darkness  —  negative  apostrophe. 
(After  STAHL.) 


§4]  PHOTOTAXIS  AXD  PHOTOPATHY  191 

interval  is  a  region  of  relatively  high  intensity  (Fig.  56,  6)  ; 
in  aquatic  plants  the  epistrophie  interval  occurs  in  a  region 
of  low  intensity  (Fig.  56,  1  and  2) ;  and  in  shade-loving 
aerophytes  in  an  intermediate  position  (Fig.  56,  4  and  5). 
One  may  say  that  every  species  is  attuned  to  a  certain  intensity 
and  range  of  light,  in  which  epistrophe  occurs,  just  as  in 
swarm-spores  there  is  a  certain  intensity  and  range  of  light  in 
which  positive  phototaxis  occurs,  and  that  attunement  depends 
upon  the  conditions  to  which  the  organism  has  adjusted  itself 
through  living  in  them. 


FIG.  56.  —  A  diagram  of  MOORE'S  photrum,  showing  for  six  spaces  the  epistrophie 
interval  (shaded  region).  1.  Anacharis  (Elodea)  canadensis,  "  water- weed." 
2.  Lemna  trisulca.  3.  Saxifraga  granulata  (position  of  positive  critical  point). 

4.  Oxalis   acetosella    (position    of    negative    critical    point    only  approximate). 

5.  Pteris  critica  (positive  critical  point).     6.  Pyrethrum  sinense  (garden  Chry- 
santhemum).    -+-  indicates  the  brighter  end  of  the  photrum. 

Concerning  the  question  of  the  mechanism  of  the  movement 
of  the  chlorophyll  grains,  there  is  much  difference  of  opinion. 
It  is  urged  on  the  one  hand  that  the  chlorophyll  grains  move 
actively  to  attain  their  new  positions,  and,  on  the  other,  that 
they  are  passively  carried  by  the  cell  currents.  Of  these  two 
views  analogical  reasons  are  perhaps  the  strongest  for  preferring 
the  second. 

As  to  the  question  in  how  far  these  movements  can  be 
regarded  as  adaptive,  we  may  say  that  STAHL  believed  that 
they  regulate  the  relation  between  intensity  of  sunlight  and 
assimilating  area,  so  that  the  quantity  of  assimilation  shall  not 
become  too  great.  HIEKONYMTJS  ('92,  p.  466)  considers  them  to 
be  for  the  purpose  of  screening  the  nucleus.  MOORE  (p.  222), 


192 


LIGHT   AND   PROTOPLASM 


[CH.  VII 


however,  chiefly  from  a  consideration  of  vegetative  apostro- 
phe, has  been  led  to  the  conclusion  "  that  the  movements  of 
chlorophyll  have  no  relation  whatever  to  benefit  or  injury 
experienced  by  the  grains,  nor  necessarily  to  the  well-being  of 
the  protoplasm." 

/3.  The  Rearrangement  of  Pigment  in  Animal  Cells  in  Response 
to  Light.  —  One  of  the  striking  cases  of  this  effect  of  light  is 
seen  in  the  pigment  cells  of  the  skin  of  the  chameleon,  as 
described  by  KELLER  ('95,  pp.  144,  162).  He  has  found  that 
the  dark  color  of  the  (illuminated)  skin  is  due  to  the  rich 


ll 


cu.  ep. 


FIG.  57. — Vertical  section  through  a  black  dermal  papilla  of  Chamaeleo  vulgaris. 
ep,  epidermis;  CM,  cutis;  p,  black  pigment  cells;  p',  processes  of  the  cells  con- 
taining pigment;  yr,  yellow  pigment  cells.  (After  KELLER,  '95.) 

branching  at  the  base  of  the  epidermis  of  black  pigment  cells 
lying  deep  in  the  cutis  (Fig.  57).  In  the  dark,  the  pigment 
granules  stream  out  of  the  branches  into  the  cell  body,  but  the 
branches  themselves  are  undisturbed  (Fig.  58).  So  long  as 
the  black  pigment  has  this  central  position,  the  skin  appears 
whitish.  The  light,  on  the  contrary,  causes  the  pigment,  which 
is  probably  carried  passively  in  the  plasma,  to  move  centrifu- 
gally.  Whether  the  direct  response  to  light  of  the  pigment 
cells  of  the  frog,  as  described  by  STEINACH  ('91),  is  of  the 
same  nature,  or  due  to  contractions  of  the  pigment  cells,  re- 
mains to  be  determined. 

Again,  in  the  retina  of  the  compound  eyes  of  Arthropoda, 


§4] 


PHOTOTAXIS  AND  PHOTOPATHY 


198 


we  find  this  capacity  for  rearrangement  of  pigment  granules, 
as  EXXER  ('89  and  '91,  p.  104),  STEFAXOWSKA  ('90),  SZCZA- 
WIXSKA  ('91),  PARKER  ('95),  and  others  have  shown.  In  the 
higher  Crustacea,  for  example,  the  pigment  granules  of  the 
pigment  cells  surrounding  the  rhabdome  (or  "  spindle  ")  are,  in 
the  dark,  below  the  level  of  the  spindle.  Upon  illumination, 
however,  these  granules  migrate  (or  are  carried)  upwards,  and 
partly  envelop  the  rhabdomes:  I  believe  it  has  not  been  deter- 
mined what  rays  are  involved  in  producing  this  result.  This 
response  to  light  is  considered  to  be  an  advantageous  one,  since 


FIG.  58.  —Vertical  section  of  a  whitish-yellow  dermal  papilla ;  lettering  as  in  Fig.  57. 
p',  processes  of  black  pigment  cells  containing  no  pigment.    (After  KELLER,  '95.) 

the  pigment  thus  cuts  off  side  rays  from  the  perceptive  organ 
—  the  rhabdome. 

It  is  interesting  that  we  should  find  cells  containing  two  so 
diverse  kinds  of  pigment  as  chlorophyll  and  the  retinal  pig- 
ment responding  to  light  in  so  similar  a  fashion.  In  most  of 
the  cases,  if  not  all,  this  response  is  an  adaptive  one. 

7.  The  Migration  of  Pigment  Cells  in  the  Metazoan  Body.  — 
It  has  been  shown,  apparently  first  by  EXGELMAXX  ('85),  that 
the  pigment  cells  of  the  retina  vary  their  movements  with  the 
light.  Thus,  when  a  strong  light  is  thrown  upon  the  retina 
of  the  frog,  the  pigment  cells  send  out  pseudopodium-like 
processes  between  the  rods  and  cones,  whereas  in  the  dark  the 


194  LIGHT   AND   PROTOPLASM  [Cn.  VII 

pigment  lies  behind  all  these  elements.  Also,  among  the  Crus- 
tacea, the  protoplasm  of  the  outer  pigment  cells,  surrounding 
the  cones  of  the  compound  eye,  migrates  centripetally  in  a  strong 
light,  to  return  again  to  its  peripheral  position  in  darkness. 
These  movements  may  also  be  considered  adaptive.  They  are, 
in  addition,  movements  which  are  discharged  only  by  light. 

c.  Metazoa. — We  may  treat  of  the.  control  by  light  of  the 
movements  of  the  higher  animals  somewhat  more  summarily 
than  we  have  the  preceding  classes.  The  facts  will  be  arranged 
by  groups  in  systematic  order. 

Among  radial  animals,  Hydra  has  perhaps  been  for  the 
longest  time  an  object  for  photopathic  study.  TREMBLE  Y 
(1744,  p.  66)  had  noticed  that  Hydra  viridis,  and  even  muti- 
lated pieces  of  it,  came  to  the  light  side  of  the  vessel.  When 
tbte  light  was  admitted  only  through  a  chevron-shaped  slit,  the 
Hydras  were  later  found  aggregated  opposite  the  slit  in  the 
form  of  a  chevron.  That  it  was  not  the  warmth  of  the  sunlight 
that  attracted  was  shown  by  turning  the  slit  towards  the  cooler 
air,  whereupon  the  same  response  occurred.  The  observations 
of  TREMBLEY  showed  that  the  Hydras  did  not  move  in  as  straight 
a  line  as  possible  towards  the  light  (they  must,  of  course,  follow 
a  firm  substratum),  but  gradually  wandered  towards  it.  The 
response  of  Hydra  must  therefore  be  considered  as  photopathy. 
More  extensive  studies  were  made  upon  Hydra  by  WILSON  ('91), 
who  found  that  Hydra  fusca  is  likewise  responsive  to  light,  and, 
indeed,  photophil  with  reference  to  diffuse  daylight,  and  photo- 
phob  to  direct  sunlight.  And  it  can  be  shown  that  it  is  an 
advantage  to  Hydra  to  be  photophil,  since  many  of  the  Ento- 
mostraca  upon  which  it  feeds  are  phototactic. 

Besides  Hydra,  I  know  of  only  one  case  of  response  by  Cce- 
lenterata  to  light.  The  larvae  of  the  sponge  Reniera  are  said 
(MARSHALL,  '82,  p.  225)  to  flee  from  the  light,  —  probably 
negative  phototaxis. 

Among  Echinodermata,  Asteracanthion  rubens  (GRABER,  '85, 
p.  155)  appears  to  be  photophil,  and  Asterina  gibbosa  (DRIESCH, 
'90,  p.  155)  to  be  photophob. 

Although,  as  we  have  seen,  some  radial  animals  may  respond 
to  light,  the  phenomenon  is  more  wide-spread  in  the  bilateral 
groups,  —  flatworms,  annelids,  crustaceans,  insects,  molluscs, 


PHOTOTAXIS  AND  PHOTOPATHY 


195 


and  Vertebrates.  The  results  of  experiments  may  here  be 
given  in  tabular  form.  Unless  otherwise  stated,  the  light  is  sup- 
posed to  be  diffuse  daylight,  and  the  response  to  be  phototaetic. 

TABLE   XVIII 


ORGANISM. 

SENSE  OF 
RESPONSE. 

AUTHORITY 

REMARKS. 

Fresh-water  planaria  .... 

- 

LOEB,  '90,  p.  95 
DRIESCH   '90  p  155 

Polygordius  larva  

LOEB,  '93,  p.  90 

see  p.  200 

Earthworm   

{DARWIN,  '81,  p.  21 
GRABER,  '83,  p.  210 

>  photophob 

Leech  

HESSE,  '96 
LOEB,  '90,  p.  96 

+ 

{TREMBLEY,  1744,  p.  96 
BERT,  '78,  p.  989 

1  photophil  (  ?) 

Many  marine  copepoda    .  . 
Balauus,  larva    

+ 
-(or+) 
—  Cor  +) 

LUBBOCK,  '82,  '83 
DAVENPORT  and  CANNON 
LOEB,  '93,  p.  96 
GROOM  and  LOEB,  '90  p. 

) 
phototaetic 
see  p.  200 
see  p.  200 

Limulus,  larva   

160 
LOEB,  '93,  p.  83 

Idotea  tricuspidata           .  . 

-j- 

GRABER  '85  p  141 

photophil 

Diastylis  (Cuma)  rathkii    . 
Carcinus  mfenas  .         .         . 

+ 

LOEB,  '90,  p.  91 
DRIESCH   '90  p  156 

mud-inhabiting 
photophob 

Homarus  americanus,  larva 
Plant  lice    

+ 
+ 

HERRICK,  '96,  p.  189 
LOEB,  '90,  p.  55 

Blatta  germanica  (blinded) 
Musca  dom.  (?),  larva  .  .  . 
Musca  adult 

+ 

GRABER,  '83,  p.  235 
LOEB,  '90,  p.  69 
LOEB   '90  p  81 

photophob 

Musca  vomitoria,  larva    .  . 
Musca  caesar,  larva  

DAVIDSON,  '85,  p.  160 
POUCHET,  '72,  p.  113 

Eristalis  teuax,  larva    .  .  . 
Lepidoptera  adult 

_|_ 

POUCHET,  '72,  p.  129 
(  SEITZ,  '90,  p.  337 

Lepidoptera  larva 

-{_ 

!  LOEB,  '90,  p.  46 
|  LOEB,  '90,  p.  51 

see  p.  197 

Ants,  after  gaining  wings  . 
Melolontha  vulgaris.    (May 
beetle) 

+ 

f  POULTON,  '87,  p.  315 
LOEB,  '90,  p.  63 

LOEB   '90  p  86 

Tenebrio  molitor,  larva   .  . 
Dentalium 

- 

LOEB,  '90,  p.  84 
LA.CAZE~DUTHIERS,    '57, 

photophob 

Rissoa  octona 

-i_ 

p.  25 
GR  \BER   '85  p.  144 

photophil 

Littoriua  rudis    

DRIESCH,  '90,  p.  155 

photophob 

Gasterosteus  spinachia.  .  . 
Triton   

- 

GRABER,  '85,  p.  148 
GRABER,  '83,  p.  221 

photophob 

Froo-   . 

LOEB   '90  p.  90 

196  LIGHT  AND  PROTOPLASM  [Ce.  VII 

A  study  of  this  table  reveals  the  fact  that,  in  general,  organ- 
isms which  live  in  shady  places  or  in  the  dark  are  negatively 
phototactic  or  photopathic,  while  those  living  in  the  light  are 
positively  phototactic  or  photopathic.  Thus  most  fresh- water 
planarians  and  leeches  are  inhabitants  of  shady  pools.  Polynoe 
is  generally  found  in  dark  retreats,  the  earthworm  and  fly 
larvae  are  lovers  of  the  dark,  and  shell-molluscs  are  for  the 
most  part  enclosed  in  cases  impervious  to  light.  On  the  other 
hand,  Daphnia  is  found  largely  in  open  pools,  larvae  of  Lepi- 
doptera  and  many  adult  insects  live  in  the  sun.  Into  this 
general  rule  there  are  some  cases  which  do  not  so  obviously  fall. 
But  we  have  little  data  concerning  the  habits  of  the  races  em- 
ployed and  the  absolute  intensity  of  light  used,  so  that  these 
cases  may  perhaps  be  only  apparent  exceptions.  One  clear 
exception  is  that  of  the  mud-inhabiting  Diastylus,  which  is  4- 
phototactic. 

3.  The  General  Laws  of  Phototaxis  and  Photopathy.  —  Under 
this  head  we  shall  consider :  (a)  the  sense  of  the  response ; 
(6)  the  effective  rays ;  (c)  prototaxis  vs.  photopathy ;  (cT)  the 
mechanics  of  response  to  light. 

a.  The  Sense  of  the  Response.  —  In  considering,  now,  more 
generally,  the  effect  of  daylight  upon  the  direction  of  loco- 
motion of  organisms,  we  must  recognize  that  the  sense  of 
response  (whether  +  or  — )  depends  upon  internal  conditions 
and  external  conditions  —  upon  the  quality  of  the  protoplasm 
and  the  nature  of  the  environment.  Let  us  consider,  first,  the 
dependence  upon  internal  conditions. 

We  find  that,  under  similar  external  conditions,  different 
organisms  respond  differently.  For  example,  many  Oscillariaa 
(p.  184)  are  positively  phototactic  even  in  direct  sunlight; 
whilst  even  moderately  strong  light  will  repel  many  diatoms. 
In  fact,  we  find  that  a  positively  phototactic  or  photopathic 
organism  is  such  only  in  the  presence  of  a  certain  intensity  of 
light.  When  the  intensity  is  diminished  below  a  certain  point, 
no  response  will  occur.  When,  on  the  other  hand,  the  intensity 
is  increased  above  a  certain  point,  the  organism  moves  away 
from  the  source  of  light.  There  is  a  certain  range  of  intensity 
in  which  alone  the  positive  responses  occur.  The  position  and 
the  extent  of  this  positively  phototactic  range  vary  for  the 


§  4]  PHOTOTAXIS  AND  PHOTOPATHY  197 

different  species,  —  they  are  closely  correlated  with  the  condi- 
tions of  light  in  which  the  organism  has  been  reared.  As  a 
result  of  these  conditions,  we  may  say  that  each  organism  is 
attuned  to  its  peculiar  range  and  intensity  of  light. 

Upon  the  ground  of  this  difference  in  attunement  may  be 
explained  the  remarkable  difference  in  behavior  of  butterflies 
and  moths  to  light.  It  is  well  known  that  butterflies  fly 
towards  even  the  strongest  sunlight,  whilst  moths  are  secluded 
during  the  daytime,  but  at  night  fly  towards  the  candle-light. 
LOEB  ('90,  p.  46)  has  performed  some  experiments  with  these 
insects,  which  I  will  cite  in  detail. 

EXPERIMENT  1.  —  (a)  Sphinx,  Bombyx,  and  other  moths  were  kept  in  a 
large  glass  cage  in  a  room  illuminated  only  by  daylight.  As  darkness  came 
on,  the  inoths  began  to  fly  towards  that  side  of  the  cage  which  was  next  the 
window.  Again  (6),  pupse  of  nocturnal  moths,  left  in  a  room,  emerged  during 
the  night,  and  were  always  found  in  the  morning  at  the  closed  window  of 
the  room.  Finally  (c),  a  nocturnal  moth,  made  to  fly  in  the  daytime,  directed 
its  way  to  the  window.  Thus,  nocturnal  moths  are  positively  phototactic 
to  diffuse  daylight  as  well  as  candle-light. 

EXPERIMENT  2.  —  Hawk-moths  were  brought  into  a  room  with  the  single 
window  at  one  end,  and  a  petroleum  lamp  at  the  opposite  end.  It  was 
found  that,  as  twilight  came  on,  the  moth  flew  to  the  window,  or  to  the  light, 
according  to  the  relative  intensity  of  the  one  or  the  other  at  the  point  where 
the  moth  was  liberated.  Thus,  there  is  no  preference  for  artificial  light. 

The  conclusion  at  which  LOEB  arrived  was  that  these  moths 
undergo  a  diurnal  variation  in  responsiveness  to  light,  which 
corresponds  to  the  change  from  day  to  night.  But  the  fact 
that,  in  experiment  1  c,  nocturnal  moths  flew,  in  the  daytime, 
towards  the  diffusely  lighted  window,  throws  a  doubt  upon  this 
interpretation.  All  the  facts  are  equally  well  explained  upon 
the  following  ground :  Butterflies  are  attuned  to  a  high  intensity 
of  light,  moths  to  a  low  intensity ;  so  that  bright  sunlight, 
which  calls  forth  the  one,  causes  the  other  to  retreat.  On  the 
other  hand,  a  light  like  that  of  a  candle,  so  weak  as  not  to 
stimulate  a  butterfly,  produces  a  marked  response  in  the  moth. 
We  shall  consider,  in  a  moment,  the  cause  of  these  differences 
in  light  attunement. 

We  have  seen  that  one  internal  condition  modifying  response 
is  the  racial  quality  of  attunement.  A  second  is  that  of  period 
of  life.  Thus,  LOEB  ('90,  p.  56)  has  found  that,  at  the  intensities 


198  LIGHT  AND  PROTOPLASM  [Cii.  VI! 

employed,  the  wingless  plant  lice  were  hardly  responsive  to 
light.  The  winged  form  was  markedly  positively  photo  tactic. 
So,  likewise,  in  the  case  of  ants  (LoEB,  '90,  p.  63),  during  the 
period  of  the  marriage  flight  the  males  and  females  (1ml  not 
the  workers)  are  strongly  positively  phototactic,  but  after  that 
period  they  show  themselves  neutral.  The  case  of  the  house- 
fly, Musca,  is  interesting,  since  the  larva  and  adult  are  photo- 
tactic  in  opposite  senses  (see  table).  In  most  of  these  cases, 
the  difference  in  responsiveness  is  associated  with  a  difference 
in  habit. 

The  sense  of  response  depends,  also,  as  we  have  seen,  upon 
external  conditions.  In  this  regard,  the  immediately  preceding 
conditions  of  light,  the  temperature,  the  concentration,  and  the 
supply  of  oxygen  have  important  effects.  We  shall  consider, 
in  order,  the  action  of  these  conditions. 

Light  can  modify  the  response  to  light;  thus,  GROOM  and 
LOEB  ('90)  have  shown  that  the  nauplii  of  Balanus,  as  well  as 
other  pelagic  animals,  come  to  the  surface  of  the  sea  during 
the  night,  but  descend  before  the  strong  sunlight.  This  does 
not  indicate  merely  a  low  light-attunement  of  the  race  ;  for 
nauplii  exposed  to  sunlight  in  the  early  afternoon  are  all  posi- 
tively phototactic,  and  only  gradually,  as  the  day  progresses, 
move  from  the  sunny  window,  until,  finally,  even  as  dusk 
approaches,  all  are  found  on  the  side  away  from  the  window. 
Nor  have  we  here  to  do  with  a  diurnal  change  in  the  sense  of 
the  response.  For  if  a  culture  is  kept  in  the  dark,  it  is  found 
to  be  at  first  positively  phototactic  at  whatever  time  of  clay  it 
is  exposed  ;  only  later  acquiring  the  negative  phototaxis.  In 
the  same  way,  when  the  young  Balanus  lar\  a>  leave  the  interior 
of  the  shell  of  the  parent,  they  are  at  first  positively  photo  tact  ic  : 
but  after  being  in  the  light  for  from  ^  to  2  hours,  they  become 
negatively  phototactic.  The  more  intense  the  light,  the  quicker 
its  effect. 

Another  observation  upon  the  nauplii  is  representative  of  a 
new  class  of  light  effects.  When  nauplii  which  have  become 
negatively  phototactic  through  exposure  are  covered  for  a  t'e\\ 
minutes,  and  then  suddenly  again  exposed  to  light,  they  move 
momentarily  towards  the  light,  and  then  begin  their  negative 
movement  again.  Somewhat  similar  are  the  results  obtained 


§4]  PHOTOTAXIS   AND   PHOTOPATHY  199 

by  STRASBURGER  ('78,  p.  574)  on  Ulothrix  spores,  which  are 
positively  phototactic  in  a  weak  light.  While  responding  to 
such  a  light,  they  do  not,  however,  turn  at  once  when  a  light 
of  repelling  intensity  is  thrown  upon  them.  So,  also  (p.  600), 
when  Hsematococcus  is  responding  to  indigo  light,  the  inter- 
position of  red  glass  does  not  at  once  cause  it  to  turn  from  its 
path.  In  all  these  cases,  the  immediately  preceding  condition 
of  light  continues  to  exert  an  action  which  modifies  the  response. 

Closely  allied  are  the  results  obtained  by  VERWORN  ('89, 
p.  T>0)  upon  the  diatom,  Navicula  brevis,  which  is  attuned  to 
only  the  faintest  light.  When,  however,  a  culture  had  been 
ivured  by  a  window  for  two  weeks,  the  attunement  to  light 
had  been  so  raised  that  now  a  slight  degree  of  positive  photo- 
taxis  took  place  in  diffuse  light.  We  have  in  these  facts 
examples  of  a  phenomenon  which  we  have  observed  in  the 
art  ion  of  other  agents.  It  is  one  expression  of  the  acclimatiza- 
tion of  organisms  to  the  peculiar  conditions  of  their  environ- 
ment. We  have  just  seen  that  every  organism  has  its  optimum 
intensity  of  light  for  metabolism  and  response,  and  that  this 
optimum  is  very  varied;  but,  throughout,  one  law  holds. 
Organisms  which  are  accustomed  to  live  in  strong  light  have 
a  high  optimum  intensity;  and  those  accustomed  to  live  in 
a  weak  light  have  a  low  optimum  intensity.  This  relation 
is,  indeed,  so  close  as  to  raise  the  suspicion  that  the  normal 
intensity  of  the  light  has  determined  the  optimum.  And  this 
suspicion  is  confirmed  by  the  experimental  evidence  just  cited. 
Now,  since  the  position  of  the  optimum  is  usually  advantageous, 
we  may  conclude  that  light  can  so  modify  protoplasm  as  to 
adapt  it  for  the  conditions  in  which  it  is  living. 

We  now  pass  to  the  consideration  of  the  effect  of  tempera- 
ture upon  response.  This  effect  was  noticed  by  STRASBURGER 
('78,  p.  605)  in  the  swarm-spores  of  Haematococcus,  Ulothrix. 
etc.,  which,  at  a  temperature  of  16°  C.  to  18°  C.,  gather  at  the 
side  of  the  drop  next  to  the  window.  If,  now,  they  are  sub- 
jected to  a  temperature  of  40°  C.,  the  intensity  of  the  light 
being  constant,  they  migrate  to  the  opposite  side.  On  the 
other  hand,  at  a  temperature  of  35°,  the  +  aggregation  is  more 
complete  than  at  16°  to  18°.  Control  experiments  with  emul- 
sions satisfied  STRASBURGER  that  this  change  is  not  due  to 


200  LIGHT  AND  PROTOPLASM  [Cn.  VII 

currents  in  the  water,  but  is  a  truly  vital  phenomenon.  That 
it  is  such  is  indicated  also  by  the  following  curious  behavior. 
If  swarm-spores  which  normally  aggregate  at  18°  towards  the 
positive  side  of  the  drop,  are  suddenly  brought  to  18°  from  30°, 
they  appear,  for  a  moment,  negative.  Conversely,  if  swarm- 
spores  which  normally  aggregate  at  30°  towards  the  negative 
side  of  the  drop  are  suddenly  brought  from  8°  to  30°,  they  ap- 
pear, for  a  moment,  positive.  Thus,  the  immediately  preceding 
culture-temperature  affects  the  sense  of  the  response. 

The  results  obtained  by  STKASBURGER  have  been  in  part 
confirmed  by  other  authors  in  other  species. 

GROOM  and  LOEB  ('90,  pp.  166,  172)  state  that  in  the  case  of  the  nauplii 
of  Balanus  —  "at  a  higher  temperature,  for  instance  25°  C.,  the  phenomena 
[of  phototaxis]  are  run  through  more  sharply  and  quickly  than  at  a  tempera- 
ture of  about  15°";  and  again,  "we  often  succeeded  in  suddenly  changing 
the  sense  of  the  heliotropism  of  the  larva  by  a  sudden  change,  of  only  a  few 
degrees,  in  the  temperature  of  the  water."  This  statement  is  unfortunately 
so  vague  as  to  say  little  more  than  this,  that  temperature  influences  the 
response.  MASSART  ('91,  p.  164)  remarks,  incidentally,  that  the  flagellate 
Chromulina  is  +  phototactic  at  20°  C.,  but  —  phototactic  at  5°  C.  LOEB 
('93,  pp.  90,  96)  obtained  a  result  with  Polygordius  larvse  and  Copepoda 
which  seems,  at  first  sight,  the  opposite  of  STRASBURGER'S.  Polygordius 
larvae,  negatively  phototactic  at  16°,  were  gradually  cooled  to  6°,  at  which 
temperature  they  began  to  move  rapidly  towards  the  +  side  of  the  vessel. 
As  the  temperature  gradually  rose  they  became  —phototactic  again.  Indi- 
viduals which  were  (abnormally)  +  phototactic  at  17°' to  24°,  when  raised 
gradually  to  29°  became  —  phototactic.  Sudden  diminution  of  temperature 
within  the  limits  at  which  response  occurs  did  not  change  the  sense  of  their 
response.  Thus,  negative  individuals  brought  suddenly  from  23°  to  13° 
remained  negative.  Exactly  parallel  results  concerning  the  relation  of 
temperature  and  response  were  obtained  by  LOEB  from  Copepoda. 

All  results  may  be  harmonized  in  the  expression  :  Diminu- 
tion of  temperature  below  the  normal  causes  reversal  of  the 
normal  response ;  elevation  of  the  temperature  to  near  the 
maximum  accelerates  the  normal  response.  The  point  of 
light  attunement  varies  with  the  temperature.* 

Not  only  light  and  heat,  but  also  the  concentration  of  the 
medium  affects  light  attunement.  We  are  indebted  to  LOEB 

*  It  follows  from  these  experiments  that  it  is  necessary  in  any  phototac- 
tic investigation  to  regard  not  only  the  intensity  of  the  light,  but  also  the 
temperature. 


§4]  PHOTOTAXIS  AND  PHOTOPATHY  201 

('93,  pp.  94,  96)  for  information  on  this  subject.  Negatively 
phototactic  Polygordius  larvae  were  placed  in  sea  water  to 
which  1%  to  1.3%  XaCl  had  been  added.  They  now  appeared 
positively  phototactic.  Positively  phototactic  individuals,  on 
the  other  hand,  placed  in  sea  water  diluted  with  40%  to  60% 
fresh  water  became  negatively  phototactic.  Similar  results 
were  obtained  with  Copepoda.  Thus  increased  concentration 
rendered  -f  phototactic  (raised  light  attunement),  while  dimin- 
ished concentration  rendered  —  phototactic  (lowered  light  at- 
tunement). Increased  concentration  works,  therefore,  upon 
Polygordius  and  Copepoda,  according  to  LOEB,  like  diminished 
temperature. 

Finally,  the  chemical  condition  of  the  medium  has  an  impor- 
tant effect  on  photopathy,  as  can  be  judged  from  certain 
observations  of  EXGELMANX  ('82%  p.  391).  Various  chloro- 
phyllaceous  Ciliata,  e.g.  Stentor  viridis  and  Paramecium  bur- 
saria,  are  photopathic  only  when  the  oxygen  supply  in  the 
medium  is  below  the  normal.  In  such  media  they  are  strongly 
photophil.  This  case  is  clearly  not  a  case  of  phototaxis,  as  we 
have  just  seen  (p.  187).  The  response  is  advantageous  since  it 
brings  these  organisms  into  the  sunlight,  where  chlorophyll  can 
produce  oxygen. 

To  recapitulate  :  the  sense  of  response  in  phototaxis  is  modi- 
fied by  previous  subjection  to  light,  by  temperature,  and  by 
concentration.  These  agents  modify  the  attunement  of  the 
organism.  Any  quantitative  experiments  upon  phototaxis 
must  therefore  take  all  of  them  into  account.  Certain  chloro- 
phyllaceous  organisms  exhibit  +  photopathy,  but  only  in  an 
insufficiently  oxygenated  medium. 

From  the  foregoing  considerations  we  conclude  that  for 
every  phototactic  organism  there  are  three  ranges  of  intensity 
to  be  distinguished  :  the  positively  phototactic  range  in  which 
the  organism  moves  towards  the  light ;  below  this,  the  indiffer- 
ent range  extending  to  darkness ;  above  it,  the  negatively 
phototactic  range  extending  up  nearly  or  quite  to  the  point  of 
light-rigor.  The  limits  of  these  ranges  vary  with  both  external 
and  internal  conditions. 

b.  The  Effective  Rays.  —  We  have  hitherto  considered  chiefly 
the  action  of  white  light,  merely  referring  casually  to  the 


202  LIGHT   AND  PROTOPLASM  [Cn.  VII 

action  of  the  different  rays  of  which  it  is  composed.  We 
must  now  answer  the  question :  What  different  effects  do  the 
different  rays  have  ? 

The  effect  of  the  different  rays  in  phototaxis  is  very  clearly 
seen  in  the  various  groups  of  Protista  and  among  the  Fla- 
gellata  and  the  swarm-spores,  there  is  entire  uniformity  of 
response  according  to  the  testimony  of  COHIST  ('65,  p.  36), 
STRASBURGER  ('78,  pp.  593-599),  ENGELMAXN  ('82%  p.  398,  in 
Euglena),  and  VERWORN  ('89%  p.  49,  in  Navicula).  Here  the 
more  actinic  rays  with  shorter  and  more  rapidly  vibrating  wave, 
act  exactly  like  white  light,  whilst  the  rays  from  the  opposite 
end  of  the  spectrum  have  no  more  effect  than  darkness.  More 
precise  determinations  were  made  by  STRASBURGER  ('78,  p. 
597),  who  found  that  the  swarm-spores  of  the  alga  Botridium 
responded  to  the  blue  and  violet,  but  especially  to  the  indigo, 
whilst  the  green  and  ultra-violet  were  alike  without  effect. 
And  ENGELMANX,  by  means  of  his  microspectral  apparatus, 
was  able  to  determine  that  Euglena  responded  chiefly  to  the 
rays  X  =  0.47//.  to  X  =0.49  /-t ;  that  is,  rays  very  near  FRAUEX- 
HOFER'S  line  F.  The  colorless  Myxomycetes  agree  with  the 
chlorophyllaceous  forms,  according  to  BARAXETZKI  ('76,  p. 
332),  in  responding  to  blue  rays  only. 

Among  the  higher  organisms,  Hydra,  according  to  WILSOX, 
accumulates  especially  behind  blue  glass,  to  a  small  extent 
behind  green  glass,  and  is  entirely  indifferent  both  to  the  upper 
violet  rays  and  those  below  the  green.  The  photophil  starfish 
Astracanthion  rubens,  even  when  deprived  of  its  eyes,  was 
found  by  GRABER  to  be  "cyanophil";  even,  though  in  slight 
degree,  to  a  low  intensity  of  light.  Among  Mollusca,  GRABER 
found  that  the  photophil  Rissoa  moved  towards  the  blue  even 
when  the  intensity  of  the  blue  light  was  less  than  that  of  the  red, 
and  DRIESCH  asserts  that  the  photophob  Littorina  rudis  shuns 
only  blue  rays.  Thus,  without  multiplying  cases,  the  results 
of  experiments  may  be  summed  up  as  follows  :  positively  pho- 
totactic  or  positively  photopathic  organisms  are  such  only  in 
the  presence  of  the  blue  rays. 

There  are  some  few  observations  which  are  in  apparent  dis- 
cord with  this  conclusion.  Whether  the  ultra-violet  rays  are 
ever  active  is  a  fairly  debatable  question.  LUBBOCK  ('82, 


§4]  PHOTOTAXIS   AND  PHOTOPATHY  203 

p.  127  ;  '84,  p.  137)  showed  that  Daphnia  and  some  ants  are 
very  sensitive  to  the  violet  rajs,  and  GRABER  ('83,  p.  214) 
found  that  the  photophob  earthworm  withdraws  from  ultra- 
violet rays.  This  result  is  unusual,  however,  for  most  experi- 
menters have  agreed  with  this  much  of  BERT'S  ('78,  p.  989) 
conclusions,  that  "  the  animals  see  .  .  .  only  those  rays  which 
we  ourselves  see,"  or,  better,  that  the  range  of  irritability  of 
the  protoplasm  of  our  retina  is  as  great  as  that  of  any  other 
protoplasm. 

Below  the  blue,  some  authors  have  believed  the  yellow  rays, 
the  brightest  of  the  spectrum,  to  be  prevailingly  photopathic. 
Thus  both  BERT  ('68,  p.  381)  and  LTJBBOCK  ('83,  p.  214)  find 
that  Daphnia  accumulates  especially  in  the  yellow  and  green 
parts  of  the  spectrum.  Regarding  these  results  I  have  only 
the  comment  that  they  need  further  confirmation. 

c.  Phototaxis  vs.  Photopathy.  —  We  have  hitherto  assumed 
the  existence  of  two  dissimilar  sorts  of  locomotor  response  to 
light  —  phototaxis  and  photopathy.  Phototaxis  we  defined  as 
migration  in  the  direction  of  the  light  rays,  and  photopathy  as 
migration  towards  a  region  of  greater  or  less  intensity  of  light. 
Are  we  justified  in  making  this  distinction? 

The  chief  ground  for  this  distinction  is  the  existence  of  two 
sorts  of  phenomena  which,  not  having  been  generally  recog- 
nized as  different,  have  led  to  extensive  discussion.  The  best- 
established  of  these  phenomena  is  phototaxis,  which  was  proved 
to  exist  by  certain  crucial  experiments  of  STRASBURGER  on 
Protista,  and  of  LOEB  on  Metazoa.  Mr.  W.  B.  CANXON  and 
I  have  used  STRASBURGER'S  methods  on  Daphnia,  and  con- 
firmed his  results.  Figure  59  gives  a  view  of  our  apparatus, 
which  was  essentially  the  same  as  STRASBURGER'S.  It  con- 
sisted of  a  hollow  prism  P,  containing  a  dark  solution  and 
placed  over  the  trough  T,  with  its  organisms.  STRASBURGER 
('78,  p.  585)  put  swarm-spores  of  Botrydium  and  Bryopsis  into 
the  trough,  and  reflected  the  light  perpendicularly  through  the 
prism  upon  the  trough.  There  was  now  a  perfect  gradation  in 
intensity  from  the  thick  end  to  the  thin  edge  of  the  prism. 
Yet  the  organisms  showed  no  tendency  to  aggregate  at  the 
clearer  end.  The  light  was  now  permitted  to  enter  the  trough 
obliquely,  the  thicker  end  of  the  prism  being  next  the  source 


T  OF   THE 

UNIVERSITY  )) 


204 


LIGHT  AND  PROTOPLASM 


[Cn.  VII 


of  light,  as  in  the  figure.  The  spores  now  moved  towards 
the  source  of  light,  i.e.  in  the  direction  of  the  inf ailing  rays 
but  constantly  into  a  region  of  less  intensity  of  light. 


FIG.  59. — Diagram  showing  the  position  of  apparatus  and  the  direction  of  the  rays 
in  an  experiment  in  phototaxis.  T,  trough  of  water  containing  organisms,  A  and 
B  its  two  ends,  M  its  middle.  P,  a  prismatic  box  containing  a  solution  of  India 
ink.  S,  screen  to  cut  off  extraneous  light.  L,  gas-lamp  having  a  WELSBACH 
burner.  Drawn  to  scale. 

LOEB'S  ('90,  p.  32)  results  were  obtained  by  the  use  of  quite 
different  methods.  In  one  case  he  employed  a  chamber  made 
of  two  test  tubes  placed  with  their  mouths  together.  One  of 
the  tubes  was  darkened  except  for  a  clear  streak  at  one  end,  c ; 
and  this  darkened  tube  was  pointed  towards  the  light,  so  that 
the  rays  fell  through  its  axis.  Although  the  clear  chamber 
was  evidently  the  brighter,  the  Porthesia  larvae  with  which 
he  experimented  moved  into  the  darkened  chamber  and  thus 
towards  the  source  of  light  (Fig.  60).  Again,  a  clear  test  tube 
containing  larvae  (Fig.  61)  was  placed  so  that  its  closed  end 
b  was  directed  towards  the  window  FF.  A  bundle  of  sun's 
rays  SS  struck  nearly  perpendicularly  the  mouth  of  the  tube  a, 
when  the  larvae  were  aggregated  at  the  beginning.  Neverthe- 
less the  larvae,  since  their  progress  in  the  direction  of  the  per- 
pendicular rays  was  soon  interrupted  by  the  walls  of  the  tube, 
moved  towards  the  window,  from  the  region  of  greater  intensity 
of  light  in  the  direction  of  rays  which  passed  more  nearly  in 
the  axis  of  the  tube.  That  this  is  not  negative  photopathy  to 
strong  light  is  indicated  by  the  fact  that  the  Porthesia  larva  is 
attuned  to  a  high  intensity  of  light.  The  evidence  would  thus 
seem  satisfactory  that  the  direction  of  migration  of  certain 


PHOTOTAXIS  AND  PHOTOPATHY 


205 


organisms  is   determined  by  "the  direction  of  the  light  rays. 
There  is,  then,  such  a  thing  as  phototaxis. 

But  is  the  direction  of  locomotion  ever  determined  by  a  dif- 
ference of  intensity  of  light  in  adjacent  regions,  without  refer- 
ence to  the  direction  of  the  light  rays  ?  Whole  series  of  obser- 
vations make  this  probable ;  for  a  migration  to  a  definite  part 
of  the  trough  has  followed  unequal  illumination  by  rays 
perpendicular  to  the  trough.  Thus  LUBBOCK  found  that 


JF 


FIG.  60.  — Two  test  tubes  a  and  b,  containing  Porthesia  larvae  c,  which  move  towards 
the  window  FF,  although  in  doing  so  they  pass  from  a  brighter  to  a  darker  region. 

(LOEB,   '90.) 

FIG.  61.  —  Diagram  to  show  how  Porthesia  larvae  move  in  the  test  tube  ab  towards 
the  window  FF,  although  in  doing  so  they  leave  the  part  of  the  tube  more  brightly 
illumined  by  the  sun's  rays  SS.  (LOEB,  '90.) 

Daphnias,  placed  in  a  trough  nearly  perpendicular  to  the  rays 
dispersed  by  a  prism,  moved  towards  the  brighter  part  of  the 
spectrum.  GKABEB  employed  screens  of  diverse  translucency 
and  color,  which  were  placed  adjacent  to  one  another,  and 
found  that  the  organisms  tended  to  aggregate  opposite  the 
one  or  the  other.  OLTMANNS  ('92,  p.  195)  has  offered  certain 
new  experiments  pointing  in  the  same  direction.  These  experi- 
ments were  made  upon  Volvox  minor  and  Volvox  globator, 
which  were  placed  in  a  trough  between  which  and  the  source 


206 


LIGHT   AND   PROTOPLASM 


[Cn.  VII 


of  light  a  vertical  screen  was  interposed.  This  screen  formed 
one  side  of  a  wooden  box  and  consisted  of  two  glass  plates 
making  an  angle  of  2°  with  each  other,  the  interspace  being 
filled  with  a  solution  of  India  ink  in  gelatine.  When  the  sun- 
light was  let  through  this  screen,  the  individuals  in  the  trough 
behind  it  sorted  themselves  into  two  groups ;  the  partheno- 
genetic  individuals,  which  collected  opposite  the  clearer  part 
of  the  screen,  and  the  female  individuals,  with  fertilized  eggs, 
which  collected  behind  the  darker  part  of  the  screen,  each  suit- 
ing itself  to  the  intensity  of  light  to  which  it  was  attuned. 
When  the  intensity  of  the  light  was  changed,  the  organisms 
also  changed  their  positions.  Finally,  LOEB  ('93,  pp.  100-103) 

has  found  that  fresh-water  plaiia- 
rians  (Planaria  torva)  gradually 
accumulate  in  the  darker  parts  of 
the  vessel,  since  the  light  con- 
stantly stimulates  them  to  move- 
ment, and  in  their  wanderings 
they  gain  the  dark  places  by 
accident  and  there  are  at  rest. 
So  it  comes  about  that  when 
these  Planaria  are  in  a  shallow 
cylindrical  vessel  (Fig.  62,  #,  5, 
<?,  d)  in  front  of  a  window  AB, 
they  accumulate  neither  at  the 
side  towards  the  window  nor  that  away  from  it,  but  at  c  and 
c?,  where  the  side  walls  of  the  vessel  cut  off  much  of  the  light. 
All  these  cases,  then,  lead  to  one  conclusion,  that  organisms 
may  move  with  reference  to  more  or  less  intense  light  —  that 
there  is  such  a  thing  as  photopathy. 

Indeed,  a  phototactic  and  a  photopathic  response  may  be 
exhibited  by  the  same  organism.  Thus  in  CANNON'S  and  my 
experiments  Daphnia  was  found  to  be  phototactic,  although 
other  observers  have  clearly  shown  it  to  be  photopathic,  a 
result  which  we  have  not  been  able  to  disprove.  We  con- 
clude, then,  that  some  organisms  have  this  double  response 
to  light  that  they  may  move  in  the  direction  of  its  rays,  and 
that  they  may  keep  in  a  certain  intensity  of  light  to  which 
they  are  attuned. 


FIG.  62.  —  Diagram  showing  position 
taken  by  Planaria  torva  in  a  shal- 
low cylindrical  glass  vessel  a,  b, 
c,  d,  placed  opposite  a  window 
AB.  (LOEB,  '93.) 


§4]  PHOTOTAXIS  AXD   PHOTOPATHY  207 

d.  The  Mechanics  of  Response  to  Light.  —  Under  this  head 
I  shall  speak  of  the  part  of  the  protoplasmic  body  most  sensitive 
to  light,  of  the  immediate  effect  of  the  light,  and  of  the  cause 
of  this  immediate  effect. 

There  can  be  no  question  that  radiant  energy  with  rapidly 
vibrating  waves  produces  upon  all  protoplasm  a  profound  effect. 
The  question  arises,  however,  to  what  extent  in  organisms  a 
special  kind  of  protoplasm  is  differentiated  for  the  reception  of 
rays  which  result  in  a  discharge  of  the  locomotor  response. 
Certainly  such  a  differentiated  protoplasm  can  hardly  be  con- 
sidered necessary  to  the  discharge  of  such  a  response,  since 
there  is  no  morphological  evidence  of  its  existence  in  the 
responsive  amoeba.  However,  even  in  the  swarm-spores  and 
Flagellata  such  a  specialized  protoplasm  is  clearly  indicated. 
Thus  EXGELMANX  (*82a,  p.  396)  found  that  when  a  dark  band 
fell  across  the  body  of  a  swimming  Euglena,  no  reaction  occurred 
so  long  as  the  hinder  chlorophyllaceous  part  alone  was  shaded. 
When,  however,  the  clear  area  at  the  base  of  the  flagellum  was 
shaded,  a  marked  reaction  occurred.  Here,  near  the  pigment 
spot,  if  not  at  it,  is  the  specialized  light-perceiving  protoplasm. 

Similarly  specialized  protoplasm  occurs  extensively  in  the 
higher  groups  in  the  form  of  retinas;  but  there  is  much  evi- 
dence that  in  many  eyeless  Metazoa  the  whole  surface  contains 
such  light-perceiving  substances.  This  is  well  known  to  be  the 
case  in  the  earthworm  (cf.  HESSE,  '96).  According  to  DUBOIS, 
('89,  p.  233),  the  siphon  of  the  boring  mussel  Pholas  dactylus 
contracts  at  the  least  variation  of  light  intensity  upon  the  skin. 
Similarly,  other  Lamellibranchia  (Ostea,  Unio,  Venus)  close 
their  valves  (\AGEL,  '96,  p.  58).  Blinded  Helix  are  said  by 
WILLEM  ('91,  p.  248)  and  NAGEL  ('96,  p.  19)  to  be  similarly 
sensitive.  The  lamellibranch  Psammobia,  the  blind  Proteus 
anguiiius,  and  the  blinded  Triton  cristatus  are  irritated  by  rays 
of  light,  especially  the  blue  rays,  falling  upon  the  skin  (NAGEL, 
'96,  p.  22;  GRABER,  '83,  p.  233;  DUBOIS,  '90,  p.  358).  Thus, 
in  many  Metazoa,  protoplasm  sensitive  to  light  is  of  widespread 
occurrence,  outside  of  the  retina.* 

The  immediate  visible  effect  of  light  upon  the  organism  differs 

*  For  an  extended  list  of  cases  of  such  dermatoptic  reaction,  see  NAGEL,  '96. 


208  LIGHT  AND  PROTOPLASM  [Cn.VII 

according  to  the  form  of  the  organism.  In  elongate,  antero- 
posteriorly  differentiated  animals  the  first  visible  phototactic 
response  is  the  orientation  of  the  organism's  axis  in  the  direc- 
tion of  the  impinging  ray,  and  with  the  head  end  directed 
towards  the  source  of  light,  or  from  that  source,  according  as 
the  organism  is  positively  or  negatively  phototactic.  The 
orientation  is  the  more  precise  and  the  retention  of  the  position 
the  more  sure  the  nearer  the  light  approaches  the  optimum 
(attractive)  or  maximum  (repellent)  intensity,  as  the  case  may 
be.  If  two  rays  of  different  intensities  making  an  angle  with 
each  other  fall  upon  the  organism,  it  apparently  moves  in  the 
direction  of  the  intenser  ray,  if  free  to  do  so.* 

In  Amoeba,  without  differentiated  axes,  the  effect  of  the  ray 
of  light  is  to  determine  the  position  of  the  centrifugal  stream- 
ing by  which  a  pseudopod  is  thrown  out  away  from  the  light  ; 
and  the  streaming  continues  in  this  single  direction  so  long  as 
conditions  do  not  change.  Thus  the  locomotion  is  in  a  straight 
line,  lying  in  the  ray  of  light. 

Light  not  merely  determines  the  direction  of  the  axis  but 
the  position  of  the  head  end.  As  we  have  seen  (p.  196)  this 
determination  of  the  position  of  the  head  depends  upon  the 
attunement  of  the  organism,  a  quality  which  in  turn  varies 
with  certain  internal  and  external  conditions.  Acting  upon  a 
"  highly  attuned "  protoplasmic  mass,^light  will  cause  orienta- 
tion in  one  sense  ;  upon  "  lowly-attuned  "  protoplasm,  an  orien- 
tation in  the  opposite  sense. 

Whether  light  has  any  other  effect  than  that  of  orientation  of 
the  body  is  a  mooted  question.  STRASBURGER  ('78,  p.  577)  and 
LOEB  ('90,  p.  109)  recognize  that  migration  from  one  point  to 
another  is  more  rapid  in  strong  light  than  in  weak,  but  believe 
this  difference  in  rate  of  migration  is  wholly  explicable  upon 
the  ground  that  the  orientation  is  more  precise  in  the  stronger 
light,  that  there  is  less  wandering  from  side  to  side.  Some  ex- 
periments made  by  Mr.  CANNOX  and  me  upon  Daphnia  seem  to 
confirm  this  view  and  at  the  same  time  afford  quantitative  data 
upon  the  degree  of  hastening.  Thus  in  18  trials  Daphnia 

*  This  statement  is  provisional  only.  It  seems  to  follow  from  the  experiments 
of  LOEB  made  upon  moths  and  described  on  page  197.  The  point  is  worthy  of 
detailed  comparative  study. 


§4]  PHOTOTAXIS   AND   PHOTOPATHY  209 

required,  to  travel  18  cm.  in  full  light,  15%  longer  time  than 
the  same  individual  required  in  light  ^  as  strong.  Since  the 
increased  time  was  only  15%  instead  of  300%,  as  it  should  be 
were  rate  proportional  to  intensity,  it  seems  probable  —  a  con- 
clusion confirmed  by  the  direct  observation  of  the  organisms  in 
the  trough  —  that  the  slower  rate  in  the  weaker  light  is  due  to 
less  precise  orientation.  How  would  the  rate  be  influenced  by 
two  lights  of  different  intensities  acting  from  opposite  direc- 
tions ?  Upon  this  matter  we  have  no  experimental  data. 

Light,  then,  serves  to  orient  the  organism ;  but  how  ?  This 
again  leads  us  to  the  general  question  of  the  cause  of  the  tactic 
response,  —  a  question  which  must  be  referred  to  a  later  chap- 
ter. Certain  special  considerations  may,  however,  be  introduced 
here.  Let  us  first  think  of  the  way  in  which  light  acts  on  the 
negatively  phototactic  (and  photopathic  ?)  earthworm.  Repre- 


LOW  LIGHT  ATTUNEMENT 


LOW  LIGHT  ATTUNEMENT 

FIG.  63.  — Diagram,  representing  sunlight  (SS)  falling  upon  an  elongated,  bilateral 
organism  (represented  by  the  arrow)  whose  head  is  at  A.     (Original.) 

sent  the  worm  by  an  arrow  whose  head  indicates  the  head  end 
(Fig.  63,  A).  Let  solar  rays  SS  fall  upon  it  horizontally  and 
perpendicularly  to  its  axis.  Then  the  impinging  ray  strikes  it 
laterally,  or,  in  other  words,  it  is  illuminated  on  one  side  and 
not  on  the  other.  Since,  now,  the  protoplasm  of  both  sides  is 
attuned  to  an  equal  intensity  of  light,  that  which  is  the  less 
illuminated  is  nearer  its  optimum  intensity.  Its  protoplasm  is  in 
a  phototonic  condition.  That  which  is  strongly  illuminated  has 
lost  its  phototonic  condition.  Only  the  darkened  muscles,  then, 
are  capable  of  normal  contraction;  the  brightly  illuminated 
ones  are  relaxed.  Under  these  conditions  the  organism  curves 
towards  the  darker  side  ;  and  since  its  head  region  is  the  most 
sensitive,  response  begins  there.  Owing  to  a  continuance  of 
the  causes,  the  organism  will  continue  to  turn  from  the  light 
until  both  sides  are  equally  illuminated  ;  i.e.  until  it  is  in  the 
light  ray.  Subsequent  locomotion  will  carry  the  organism  in  a 


210  LIGHT   AXD   PROTOPLASM  [Cn.  VII 

straight  line,  since  the  muscles  of  the  two  sides  now  act  simi- 
larly. Thus  orientation  of  the  organism  is  effected.  The  same 
explanation,  which  is  modified  from  one  of  LOEB  ('93,  p.  86), 
will  account,  mutatis  mutandis,  for  positive  phototaxis. 

Such  an  explanation  can  serve  only  for  elongated  organisms. 
The  case  of  the  amoeba  is  quite  different.  Here  we  must  think 
of  the  protoplasm  as  being  modified  by  a  light  ray  so  as  to  flow 
centrifugally  especially  in  that  ray,  perhaps  through  peculiar 
molecular  disturbance  wrought  by  the  ray. 

As  for  photopathic  response,  that  is  probably  to  be  accounted 
for  on  the  ground  upon  which  ENGELMANN  has  explained  the 
arrangement  of  Bacterium  photometricum  in  the  microspec- 
trum  ;  on  the  ground,  namely,  that  increased  brightness  causes 
a  movement  forwards,  that  a  diminution  in  brightness  causes  a 
movement  backwards,  or  vice  versa,  thus  resulting  in  the  accu- 
mulation of  the  organisms  in  the  darker  or  lighter  parts  of  the 
field. 

To  summarize,  then,  light  acts  directly  either  through  differ- 
ence in  intensity  on  the  two  sides  of  the  organism,  or  by  the 
course  the  rays  take  through  the  organism.  Difference  in 
intensity  of  light  may  also  determine  the  position  of  organisms 
with  reference  to  light  by  virtue  of  the  irritation  produced  by 
rapid  change  of  intensity. 

SUMMARY  OF  THE  CHAPTER 

The  study  of  the  effect  of  light  on  protoplasm  must  be  made 
quantitative  as  well  as  qualitative,  and  demands  the  use  of  appa- 
ratus for  determining  the  quality  and  intensity  of  the  light 
employed.  The  reactions  produced  by  light  upon  protoplasm 
are  undoubtedly  of  a  chemical  character,  and,  indeed,  experi- 
ments with  non-living  organic  compounds  show  that  it  has  an 
important  effect  in  synthesis,  in  analysis,  in  substitution,  in  the 
production  of  isomeric  or  polymeric  conditions,  and  in  fermen- 
tation. Since  protoplasm  consists  of  a  large  number  of  kinds 
of  organic  substances,  we  should  expect  light  to  produce  far- 
reaching  results,  the  more  so  as  it  can  penetrate  deep  into  the 
tissues  of  the  organism. 

The  effect  of  light  upon  the  general  functions  of  organisms  is 


SUMMARY  OF   THE   CHAPTER  211 

revealed  in  modifications  of  metabolism  and  of  movement,  and 
in  the  production  of  death.  Upon  metabolism  we  can  distin- 
guish an  effect  of  the  red  rays,  which  are  greatly  absorbed  by 
chlorophyll  and  are  chiefly  active  in  assimilation,  and  an  effect 
of  the  blue  rays,  which  seem  to  produce  important  chemical 
changes,  increasing  the  production  of  carbon  dioxide  in  plants, 
creating  an  electric  current  in  the  retina  as  it  falls  thereon, 
and  bleaching  visual  purple.  These  chemical  changes  become 
more  vigorous  with  increased  intensity  of  light  and  may  lead 
to  death  ;  while,  at  the  opposite  extreme,  complete  absence  of 
light  may  prove  fatal  by  withdrawing  the  necessary  thermic 
and  chemical  energy.  Again  we  find  light  sometimes  necessary 
to  movement  in  protoplasm,  at  other  times  by  its  absence  or 
too  great  intensity  inhibiting  movement,  or,  again,  by  sudden 
change  in  intensity,  creating  abrupt  changes  in  movement. 
Thus  light  undeniably  has  a  great  effect  upon  the  processes  of 
metabolism  and  movement. 

Finally,  in  those  complex  processes  involved  in  locomotion, 
light  produces  very  widespread  effects ;  for  the  direction 
(and,  though  only  indirectly,  perhaps,  the  rate)  of  locomotion 
is  influenced  in  so  important  a  way  that  when  light  is  with- 
drawn the  organism  wanders  aimlessly  about.  Of  the  various 
rays,  those  with  wave  length  =  40/,t  to  49/z  are  the  most  active 
in  controlling  locomotion.  Movement  towards  the  light  takes 
place  at  intensities  of  light  varying  greatly  with  the  species 
and  also  with  the  conditions  other  than  light  in  which  the  indi- 
vidual finds  itself,  —  two  factors  upon  which  depends  the  degree 
of  attunement.  Light  having  an  intensity  above  that  to  which 
the  organism  is  attuned  repels  the  organism.  Two  kinds  of 
effects  are  produced  by  light :  one  by  the  direction  of  its  ray 
—  phototactic  ;  the  other  by  the  difference  in  illumination  of 
parts  of  the  organism  —  photopathic. 

AVe  thus  see  that  organisms  respond  to  light,  and  that  this 
response,  exhibited  in  movements,  is  not  of  a  widely  different 
order  from  the  disturbances  produced  in  metabolism,  which  in 
turn  are  of  the  same  order  as  the  chemical  changes  produced  by 
light  in  our  laboratories  upon  non-living  substances.  In  a  word, 
response  to  light  is  the  result  of  chemical  changes  in  the  proto- 
plasm wrought  by  light. 


212  LIGHT  AND  PROTOPLASM  [Cn.  VII 


LITERATURE 

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LITERATURE  213 


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March-August,  1872. 
POULTON,  E.  B.  '87.     Notes  in  1886  upon  Lepidopterous  Larvae,  etc.     Trans. 

Ent.  Soc.  Lond.  for  1887.     pp.  281-321,  PL  X.     Sept.  1887. 
PRINGSHEIM,  N.  '80.     Ueber  Lichtwirkung  und  Chlorophyllf unction  in  der 

Pflanze.     Jahrb.  f.  wiss.  Bot.     XII,  288-437.     Taf.  XI-XXVI. 
'81.     Ueber    die   primaren   Wirkung    des   Lichtes   auf   die   Vegetation. 

Monatsber.  Akad.  Wiss.,  Berlin,  Jahre  1881.     pp.  504-534. 
RAUM,  J.  '89.     Die  gegenwartige  Stand  unserer  Kenntnisse  iiber  den  Ein- 

flusse  des  Lichtes  auf  Bacterien  und  auf  den  thierischen  Organismen. 

Zeitschr.  f.  Hygiene.     VI,  312-368. 
RAYLEIGH,   LORD,   '81.     Experiments  on  Color.     Nature.     XXV,   64-66. 

17  Nov.  1881. 
REINKE,  J.  '83.     Untersuchungen  iiber  die  Einwirkung  des  Lichtes  auf  die 

Sauerstoffausscheidung  der  Pflanzen.     I.  Mitt.  Bot.  Ztg.     XVI,  697- 

707;  713-723;  732-738. 
'84.     The  same.     II.  Mitt.  Bot.  Ztg.     XLII,  1-10;  17-29;  33-46;  49-59. 

Jan.  1884. 
SACHS,  J.  '76.     Ueber  Emulsionsfiguren   und   Gruppirung  der  Schwarm- 

sporen  ini  Wasser.     Flora.     LIX,  241-248;  257-264;  273-281. 
'60.     Ueber  die  Durchleuchtung  der  Pflanzentheile.     Sb.  K.  Akad.  Wiss., 

Wien.     XLIII,    Abth.  1.     6    Dec.  1860.     [Also  in  his  Gesammelte 

Abh.  iiber  Pflanze  n-physiol.     I,  167.] 
'64.     Wirkungen  farbigen  Lichts  auf  Pflanzen.     Bot.  Ztg.     XXII,  353- 

358,   361-367,  369-372.     Nov.,  Dec.  1864.     [Also  in   his  Ges.   Abh. 

I,  261-292.] 

'92.     Gesammelte  Abhandlungen  iiber  Pflanzenphysiologie.     I  Bd.     Leip- 
zig, Engelmann. 
SEITZ,  A.  '90.     Allgemeine   Biologic   der   Schmetterlinge.     Zool.   Jahrb. 

Abth.  f.  Syst.     V,  281-343.     19  July,  1890. 
SOROKIN,  N.  '78.     Grundziige   der  Mykologie   mit   Uebersicht   der   Lehre 

iiber  die  Infectionskrankheiten.     Bd.  I,  Hft.  1,  511  pp.     Kasan  [Rus- 
sian.    Only  the  Abstract  in  Botan.  Jahresber.     VI  (1878),  1  Abth., 

p.  471,  has  been  seen.] 
STAHL,  E.  '78.     Ueber  den  Einfluss  des  Lichtes  auf  die  Bewegungserschein- 

ungen  der  Schwarmsporen.     Verh.  phys.-med.  Ges.  Wiirzburg.     XII, 

269,  270. 


LITERATURE  217 

STAHL,  E.  '79.     Ueber  den  Einfluss  des  Lichtes  auf  die  Bewegungen  der 

Desmidien  nebst  einigen  Bemerkungen  iiber  den  richtenden  Einfluss 

des  Lichtes  auf  Schwarmsporen.     Verb,  phys.-med.  Ges.  Wiirzburg. 

XIY,  24-34. 
'80.     Ueber   den   Einfluss  von   Richtung  und   Starke  der  Beleuchtung 

auf   einige  Bewegungserscheinungen  im  Pflanzenreiche.      Bot.   Ztg. 

XXXVIII,  297  et  folg.     April-June,  1880. 
'84.     Zur  Biologie  der  Myxomyceten.     Bot.  Ztg.     XLII,  145-155,  161- 

175,  187-191.     March,  1884. 
STEFANOWSKA,  M.  '90.     La  disposition  histologique  du  pigment  dans  les 

yeux  des  Arthropodes  sous  1'influence  de  la  lumiere   directe   et   de 

Fobscurite  complete.     Recueil  Zool.  Suisse.     V,  151-200.     Pis.  VTH, 

IX.     15  July,  1890. 
STEIXACH,  E.  '91.     Ueber  Farbenwechsel  bei  niederen  Wirbelthieren  bedingt 

durch  directe  Wirkung  des  Lichtes  auf  die  Pigmentzellen.     Centralbl. 

f.  Physiol.     V,  326-330.     12  Sept.  1891. 
'92.     Untersuchungeii  zur  vergleichenden  Physiologic  der  Iris.     Arch.  f. 

d.  ges.  Physiol.     LII,  495-525.     28  July,  1892. 

STRASBURGER,  E.  '78.     Wirkung  des  Lichtes  und  der  Warme  auf  Schwarm- 
sporen.    Jena.  Zeitschr.     XII,  551-625. 
STREIT,  G.  and  FRANZ,  B.  '70.     Einwirkung  von  Chlor  auf  absoluten  Al- 

kohol  bei  Sonnenlicht.     Jour,  prakt.  Chem.     CVIH,  61,  62.     13  Jan. 

1870. 
SZCZAWIXSKA,  V.  '91.     Contribution  a  Fetude  des  yeux  de  quelques  Crus- 

taces  et  recherches  sur  les  mouvements  du  pigment  granuleux  et  des 

cellules  pigmentaires  sous  1'influence  de  la  lumiere  et  de  Pobscurite 

dans  les  yeux  des  Crustaces  et  des  Arachnides.     Arch,  de  Biol.     X, 

523-566.     31  March,  1891. 
TIMIRIAZEFF  '77.      Recherches  sur  la  decomposition  de  1'acid  carbonique 

dans  le  spectre  solaire  par  les  parties  vertes  des  vegetaux.     Ann.  de 

Chim.  et  de  Physiq.     (5)  XII,  335-396. 
'90.     Enregistrement  photographique  de  la  fonction  chlorophyllienne  par 

la  plante  vivante.     Comp.  Rend.     CX,  1346-1347.     23  June,  1890. 
TREMBLEY,  A.  1744.   Memoires  pour  servir  a  Phistoire  d'un  genre  de  polypes 

d'eau  douce,  a  bras  en  forme  de  cornes.     Leyden.     324  pp.,  13  pis. 

1744.     [The  reference  is  to  the  end  of  the  first  memoir.] 
VERWORN,  M.  '89.     (See  Chapter  I,  Literature.) 

'95.     (See  Chapter  IV,  Literature.) 
VIERORDT,  K.  '73.     Die  Anwendung  des  Spectralapparates  zur  Photometric 

der  Absorptionspectren  und  zur  quantitativen   chemischen  Analyse. 

169  pp.,  6  Taf.     Tubingen  :  Laupp. 
VOGEL,  H.  C.  '77.     Spectral-photometrische  Untersuchungen  insbesondere 

zur  Bestimmung  der  Absorption  der  die  Sonne  umgebenden  Gashiille. 

Monatsber.  Akad.  Wiss.,  Berlin.     Jg.  1877,  pp.  104-142,  Taf.  I. 
WARD,  H.  M.  '93.     Experiments  on  the  Action  of  Light  on  Bacillus  anthra- 

cis.     Proc.  Roy.  Soc.,  London.     LII,  393-400.     10  Feb.  1893. 


218  LIGHT  AND  PROTOPLASM  [Cn.  VII 

WARD,  H.  M.  '93a.     Further  Experiments  on  the  Action  of  Light  on  Bacillus 

anthracis.     Proc.  Roy.  Soc.     LIII,  23-44. 
'94.     The   Action  of  Light  on  Bacteria.     III.     Proc.  Roy.   Soc.     LIV, 

472-475. 
'94a.     Further  Experiments  on  the  Action  of  Light  on  Bacillus  anthracis 

and  on  the  Bacteria  of  the  Thames.     Proc.  Roy.  Soc.     LVI,  315-394. 
WETTSTEIN,   R.  v.   '85.     Untersuchungen   iiber  einen   neuen  pflanzlichen 

Parasiten  des  menschlichen  Kb'rpers.    Sb.  K.  Akad.  wiss.  Wien.     XCI, 

1  Abth.,  33-58. 
WILLEM,  V.  '91.     La  vision  chez  les  Gastropodes  pulmones.     Comp.  Rend. 

CXII,  247,  248.     26  Jan.  1891. 

WILSON,  E.  B.  '91.    The  Heliotropism  of  Hydra.    Am.  Nat.    XXY,  413-433. 
WINOGRADSKY,  S.  '87.     Ueber  Schwefelbacterien.     Bot.  Ztg.     XLV,  489  et 

folg.     Aug.-Sept.  1887. 
YUNG,  ]3.  '78.     Contributions  a  1'histoire  de  1'influence  des  milieux  physiques 

sur  les  etres  vivants.     Arch,  de  Zool.     VII,  251-282. 


CHAPTER  VIII 

ACTION  OF  HEAT  UPON  PROTOPLASM 

Ix  this  chapter  it  is  proposed  to  consider  (I)  briefly,  the 
nature  of  heat  and  the  general  methods  of  its  application ; 
(II)  the  action  of  heat  upon  the  general  functions  of  organ- 
isms ;  (HI)  the  temperature-limits  of  life  ;  (IV)  the  accli- 
matization of  organisms  to  extreme  temperature,  and  (V)  the 
determination  of  the  direction  of  locomotion  by  heat  —  ther- 
motaxis. 

§  1.   NATURE  OF  HEAT  AND  THE  GENERAL  METHODS  OP 
ITS  APPLICATION 

Heat  is  believed  to  be  due  to  the  vibrations  of  the  molecules 
of  bodies.  In  any  heated  solid,  fluid,  or  gaseous  mass  the 
molecules  are  in  constant  motion.  When  the  temperature 
is  increased,  the  motion  is  increased,  and  the  impacts  of  the 
flying  molecules  become  more  frequent.  If  a  vessel  containing 
Avater  is  brought  into  contact  with  warmer  air  or  warmer  fluid, 
its  molecules  fly  faster,  its  temperature  is  raised.  As  the 
motion  of  the  molecules  in  the  walls  of  the  vessel  increases, 
the  increased  motion  is  transmitted  to  the  contained  water, 
and  finally  to  the  objects  in  the  water.  Thus  the  motion  of 
the  molecules  of  an  organism  in  the  water  is  increased  with  the 
increase  of  the  temperature  of  the  water.  Heat,  as  so-called 
radiant  heat,  is  transmitted  through  space  in  straight  lines,  and 
follows  all  the  laws  of  light,  into  which  it  passes  when  the  rate 
of  wave  vibrations  becomes  rapid  enough  to  affect  the  retina. 
The  chief  effects  of  radiant  heat  were  considered  in  the  last 
chapter. 

Heat  is  an  important  element  in  all  chemical  processes.  The 
state  of  cohesion  —  solid,  liquid,  gaseous  —  and  the  ease  with 

219 


220 


HEAT   AND  PROTOPLASM 


[Cn.  VIII 


which  molecular  decomposition  and  synthesis  occur,  vary  directly 
with  it.  This  is  an  important  consideration  in  our  study  of  pro- 
toplasm, for  most  of  its  changes  are  chemical  changes. 

A  word  should  be  said  concerning  general  methods  of  apply- 
ing heat  to  protoplasm.     In  the  case  of  the  higher  plants  and 

seedlings,  the  device  of  SACHS  ('92, 
p.  117)  may  be  employed.  This 
consists  of  two  metallic  vessels,  a 
and  i  (Fig.  64),  of  similar  form, 
one  placed  inside  of  the  other,  the 
interspace  being  filled  with  water. 
Within  the  inner  vessel  is  placed 
the  pot  (£)  with  the  object  of  ex- 
perimentation. The  whole  is  cov- 
ered over  by  a  half  globe  of  glass 
(#),  extending  down  to  below  the 
level  of  the  top  of  the  pot.  The 
water  is  heated  by  a  lamp  (T)  be- 
low, by  which  means  moisture  and 
warmth  are  carried  to  the  plant. 

In  the  case  of  the  lower  organ- 
isms, brief  experiments  may  be  con- 
ducted in  shallow  aquaria  for  the 
horizontal  microscope  (Fig.  65),  like 
those  devised  by  CORI  ('93).  It  is 
preferable  to  put  inside  of  the  outer 
vessel  a  smaller  glass  vessel,  which 
shall  contain  the  organisms  and 
the  thermometer  marking  the  tem- 
perature of  the  water.  For  long- 
continued  experiments  where  con- 
stant high  temperature  is  required, 


FIG.  64.  —  Apparatus  for  study- 
ing the  effect  of  heat  upon 
germination  in  phanerogams, 
a,  the  external;  i,  the  inter- 
nal vessel,  between  which  is 
a  water  space ;  t,  flower-pot 
filled  with  earth  and  con- 
taining a  seedling  of  maize 
p  ;  h,  three  supports  for  the 
glass  bell  g ;  u,  support  for 
the  flower-pot ;  d,  tripodal 
iron  stand  carrying  the  spirit- 
lamp  /.  (From  SACHS,  '92.) 


a  warm  oven,  such  as  is  used  in  bacteriological  work,  is  essential. 
The  production  of  extremely  low  temperatures  offers  special 
difficulties.  For  temperatures  to  —  40°  or  so,  various  freezing 
mixtures  can  be  employed.  Of  these  chopped  ice  and  common 
salt  in  equal  parts  give  a  temperature  of  •  -  18°  ;  calcium  chlo- 
ride and  snow,  in  proportions  of  3  to  2,  give  —  33° ;  and  cal- 
cium chloride  and  snow,  in  the  proportion  of  2  to  1,  give  —  42°, 


§1] 


METHODS 


221 


the  initial  temperature  being  always  supposed  to  be  0°.  Far 
lower  temperatures  than  these  have  been  obtained  by  phy- 
sicists, notably  PICTET,  to  whose  work  we  shall  refer  again 


FIG.  65.  —  CORI'S  stage   aquarium.      A,  the  aquarium  proper;    T,  holder  for  the 
aquarium;   7?,  R,  slides,  with  springs.     (From  CORI,  '93.) 

(p.  240).     The  organisms  to  be  acted  upon  may  be  kept  in  an 
apparatus  (Fig.  66)  like  that  employed  by  POTJCHET  ('66). 

Throughout  this  chapter,   as  indeed  throughout  the  whole 
book,  thermometric  readings  are  given  in  Centigrade   scale, 


FIG.  66.  —  Cold  chamber  seen  in  external  view  and  in  section.  The  wall  is  composed 
of  an  inner  cylinder  containing  the  freezing  mixture  and  the  receptacle  for  the 
object  of  experimentation,  and  an  outer  cylinder  separated  from  the  inner  by  a 
packing  of  fragments  of  charcoal.  The  receptacle  containing  the  organism  is 
provided  with  a  thermometer  and  an  air  tube.  (From  POUCHET,  '66.) 


222 


HEAT  AND  PROTOPLASM 


[Cn.  VIII 


unless  otherwise  stated.  All  readings  not  designated  by  the 
—  sign  are  above  the  Centigrade  0  point.  The  point  of  abso- 
lute 0,  to  which  we  may  have  occasion  to  refer,  is  —  273°  C. 


§  2.     THE  EFFECT   OF   HEAT  UPON  THE  GENERAL  FUNC- 
TIONS OF  ORGANISMS 

Under  this  topic  will  be  considered  (1)  the  effect  upon 
metabolism,  and  (2)  the  effect  upon  movement  and  irritability. 

1.  Effect  of  Heat  upon  Metabolism.  —  Within  certain  limits 
the  relative  increase  of  temperature  leads  to  a  relative  increase 
in  the  activity  of  the  various  metabolic  processes.  This  is  well 
seen  in  those  chemical  changes  which  produce  so-called  phos- 
phorescence. Many  years  ago  MACAIRE  ('21,  p.  157)  showed 
for  fireflies,  and  ARTAUD  ('25,  p.  372)  for  the  organisms  of  the 
sea,  that  light  begins  to  appear  shortly  above  20°,  reaches  its 
maximum  intensity  at  40°  in  the  fireflies  and  35°  in  the  water 
organisms,  and  entirely  disappears  at  59°  to  62°  in  the  first 
case,  and  43°  in  the  second.  The  temperature  of  these  three 
points  —  lowest  temperature  of  metabolic  activity,  temperature 
of  greatest  activity,  and  highest  temperature  permitting  of 
activity  —  may  be  called,  respectively,  the  minimum,  optimum, 
and  maximum  temperatures  for  phosphorescence. 

The  effect  of  temperature  on  metabolism  is  seen  in  the 
absorption  of  oxygen  by  organisms.  Thus  VON  WOLKOFF  and 
MAYER  ('74)  found  that  more  oxygen  is  absorbed  by  seedlings, 
as  the  temperature  is  increased,  from  0°  to  about  35°  C.  This 
is  shown  in  the  following  table.  (From  VINES,  '86,  p.  198.) 


FIVE  NASTURTIUM  SEEDLINGS. 

FOUR  WHEAT  SEEDLINGS. 

TOTAL  AMOUNT  OF  O 
ABSORBED  PER  c.c. 

TEMPERATURE  C. 

TOTAL  AMOUNT  OF  O 
ABSORBED. 

TEMPERATURE  C. 

0.60 

22.4° 

0.10 

15.6° 

0.77 

27.0° 

0.038 

4.4° 

0.76 

30.5° 

0.067 

9.8° 

0.77 

30.0° 

0.088 

15.4° 

1.04 

35.0° 

0.022 

0.3° 

0.91 

38.2° 

0.010 

0.1° 

§2] 


EFFECT  ON  GENERAL  FUNCTIONS 


223 


Likewise  MOISSAX  (79,  p.  296)  found  that,  in  the  dark,  the 
amount  of  oxygen  absorbed  by  a  branch  of  certain  plants  varied 
with  the  temperature.  Thus  there  was  absorbed  per  hour  by 


Pimis  pinaster  (30  grammes)     . 


Agave  americana  (70  grammes) 


at  0°  C., 
at  13°, 

I  at  15°, 

f  at  11°  C., 

1  at  40°, 


0.32  c.c. 
1.30  c.c. 
1.90  c.c. 
0.54  c.c. 
5.56  c.c. 


These  experiments  serve  to  show  clearly  that  in  plants  more 
oxygen  is  absorbed  as  the  temperature  is  raised  to  the  optimum. 

The  same  result  is  obtained  from  animals  also.  Thus  TRE- 
VIRAXUS  ('31,  p.  23)  found  that  the  honey  bee  Apis  mellifica 
absorbed  at  14°  C.  1.35  Paris  cubic  inches,  and  at  27.5°,  2.77 
cubic  inches  of  oxygen.  At  the  higher  temperatures  the  bee 
was  very  active,  so  that  the  result  seems  here  somewhat  com- 
plicated by  the  increased  muscular  activity  accompanying  a 
higher  temperature,  which  invokes  a  more  rapid  respiration. 
Nevertheless,  the  phenomena  of  increased  oxygen  absorption 
with  higher  temperature  are  fundamentally  the  same  in  plants 
and  animals. 

Turning  now  to  the  process  of  excretion,  it  appears  that  the 
amount  of  CO2  evolved  by  seedlings  varies  with  the  tempera- 
ture. On  this  point  we  have  data  by  DEHERAIN  and  MOISSAX 
('74.  p.  327),  RISCHAWI  ('77),  and  others.  DEHERAIN  and 
MOISSAN  experimented  with  leaves  of  tobacco  kept  in  the 
dark.  The  same  plant  was  used  throughout  the  experiment, 
and  it  remained  throughout  in  good  condition.  In  the  follow- 
ing table  the  temperatures  are  given  in  the  first  column,  and, 
in  the  second,  the  number  of  grammes  of  CO2  produced  per 
100  grammes  of  leaves  :  — 


TEMP. 

GMS.  COj. 

TEMP. 

GMS.  CO,. 

TEMP. 

GMS.  CO2. 

TEMP. 

GMS.  COj. 

7 

0.031 

15 

0.165 

20 

0.263 

40 

0.961 

13 

0.139 

18 

0.178 

21 

0.289 

41 

1.132 

14 

0.157 

19 

0.193 

32 

0.514 

42 

1.325 

When  plotted  (with  the  temperatures  as  abscissae)  the  relation 
between  temperature  and  weight  of  CO2  produced  is  expressed 


224 


HEAT   AND   PROTOPLASM 


[CH.  VIII 


by  a  line  which  is  slightly  steeper  at  the  higher  temperatures 
than  at  the  lower.  This  change  of  steepness  is,  however,  much 
less  striking  in  the  case  of  the  etiolated  wheat  seedlings  studied 
by  RISCHAWI,  where  the  following  series  was  obtained :  - 


TEMPERATURE. 

WEIGHT  CO2  IN  Me. 

TEMPERATURE. 

WEIGHT  C02  IN  MG. 

5° 

3.30 

25° 

17.82 

10° 

5.28 

30° 

22.04 

15° 

9.90 

35° 

28.38 

20° 

12.54 

40° 

37.60 

The  evidence  from  excretion  thus  also  confirms  the  conclusion 
that  the  metabolic  processes  are  accelerated  by  raising  the  tem- 
perature to  a  certain  limit. 

The  effect  of  heat  in  the  metabolic  process  of  chlorophyll 
formation  is  shown  in  some  plants  upon  which  SACHS  ('64) 
experimented.  He  prepared  three  culture  chambers,  all  illu- 
minated by  a  north  light.  A  was  kept  at  a  high  temperature, 
namely,  30°  to  34°  C. ;  B  was  kept  at  a  temperature  of  16°  to 
20°  C.,  and  0 at  8°  to  14°  C.  Into  these  chambers  were  put  etio- 
lated seedlings  of  Phaseolus  multiflorus  (bean)  and  Zea  mais 
(maize)  which  had  been  reared  in  the  dark.  The  first  traces  of 
turning  green  appeared  in  A  after  1 J  hours ;  in  B  after  2  to  5 
hours  ;  whilst  in  C  no  trace  of  greening  appeared  until  several 
days  had  passed.  Thus  it  appeared  that  at  the  temperature  of 
8°  to  14°  C.  chlorophyll  is  hardly  produced. 

We  now  pass  to  the  consideration  of  some  Protista.  An 
indication,  at  least,  that  the  rate  of  metabolism  is  increased 
with  temperature  is  gained  from  the  increased  rapidity  of 
formation  of  the  contractile  (excreting)  vacuoles  of  Ciliata 
under  these  conditions.  Thus,  ROSSBACH  ('72,  p.  33)  found 
that  the  rapidity  of  the  rhythmic  movements  of  the  contractile 
vacuole  is  most  intimately  related  with  the  temperature  of  the 
body,  so  that  one  and  the  same  species  of  animal  under  normal 
conditions  always  has,  at  a  given  temperature,  the  same  number 
of  contractions.  From  the  number  of  the  rhythmic  contrac- 
tions one  can  therefore  draw  a  certain  conclusion  concerning 
the  existing  degree  of  temperature*  This  relation  between 


§2] 


EFFECT  ON  GENERAL  FUNCTIONS 


225 


DEGREES 
1     3     5     7     9    11  13  15  17  19  21  23   25  27   29  31  33  35 


temperature  and  interval  between  contractions  is  given  in 
Fig.  67.  We  cannot  say  that  the  increment  of  excretion  is 
exactly  equal  to  that  of  con- 
traction, but  there  is  doubtless 
a  correlation  between  the  two 
activities. 

From  all  these  facts  we  may 
conclude  that,  within  certain 
limits,  an  increase  of  tempera- 
ture increases  metabolism,  and 
a  diminution  of  temperature 
diminishes  it.  But  the  incre- 
ment in  metabolic  processes 
soon  finds  a  limit  at  a  tem- 
perature above  which  the 
metabolic  processes  begin  to 
diminish. 

2.  Effect  of  Heat  upon  the 
Movement  of  Protoplasm  and 
its  Irritability.  —  All  observers 
(DUTEOCHET,  -'37,  pp.  777, 
778;  XAGELI,  '60,  p.  77; 
SACHS,  '64;  HOFMEISTER,  '67, 
pp.  53,  54 ;  and  COHN,  '71,  for 
plant  cells;  and  KUHXE,  '59, 
p.  821  ;  and  SCHULTZE,  '63, 
p.  46,  for  Protozoa)  agree 
that  a  gradual  increase  in 
temperature  above  that  of  the 
ordinary  living  room  results, 
within  certain  limits,  in  an 


FIG.  67. — The  mean  thermal  curves  de- 
termined by  ROSSBACH  for  the  con- 
tractile vesicle  of  Infusoria.  I,  for 
Euplotes  charon ;  II,  for  Stylonychia 
pustulata;  III,  for  Chilodon  cucul- 
lulus.  The  abscissae  indicate  degrees 
of  temperature,  Centigrade,  in  two- 
degree  intervals ;  the  ordinates  give 
the  number  of  seconds  elapsing 
between  successive  contractions  of 
the  vesicle,  in  two-second  intervals. 
(From  SEMPER,  "Animal  Life.") 


increase  in  the  rate  of  movement  of  the  protoplasm.  A 
diminution  in  temperature,  on  the  contrary,  causes  a  decrease 
in  the  movement. 

For  this  acceleration  with  increased  temperature,  NAGELI 
sought  to  obtain  a  quantitative  expression.  He  measured 
the  time  consumed  at  different  temperatures  in  the  migration 
through  0.1  mm.  of  the  granules  floating  in  the  stream  of 
protoplasm  seen  in  the  end  cells  of  Nitella  syncarpa.  Some 
Q 


226 


HEAT   AND   PROTOPLASM 


[Cn.  VIII 


measurements  were  made,  also,  by  SCHULTZE,  011  Tradescantia 
hairs.  But  the  work  of  neither  of  these  equals  in  importance 
the  determinations  of  VELTEN  ('76),  which  I  propose  to  give 
in  some  detail.  He  determined  the  time  consumed  by  the 


60mm 


50mm 


40mm 


30mm 


20mm 


10mm 


50mm 


40mm 


30mm 


30mm 


10mm 


0°  5°  10°          15°         20°          25°          30°          35°          40°          4o°C. 

FIG.  68.  —  Curves  showing  the  relation  between  temperature  (abscissae)  and  rate  of 
movement  per  minute  of  the  chlorophyll  grains  floating  in  the  protoplasm  of  the 
cells  of  three  species  of  green  plants.  (Data  from  VELTEN,  '76.) 

floating  chlorophyll  grains  in  cells  of  Elodea  canadensis  and 
Vallisneria  spiralis,  or  the  small  granules  near  the  wall  of  cells 
of  Chara  in  traversing  0.1  mm.,  at  various  temperatures.  The 
results  in  modified  form  are  given  graphically  for  these  three 
species  in  Fig.  68.  In  this  figure,  the  ordinates  represent 
distance  (in  millimetres)  traversed  in  1  minute.  The  abscissae 


§2]  EFFECT   ON   GENERAL  FUNCTIONS  227 

represent  temperatures  (Centigrade)  from  0°  on  the  left  to  44° 
011  the  right.  The  rate  of  movement  increases  regularly  up 
to  a  maximum  (the  optimum),  a  rise  of  1°  C.  being  associated 
with  an  increased  rate"  of  movement  in  Chara  of  1.4  mm.  ;  in 
Vallisneria  of  0.62  mm. ;  in  Elodea  of  0.26  mm.  The  rate  of 
increase  is,  in  general,  slightly  greater  near  the  optimum. 
The  optimum  varies,  in  the  three  species,  from  34°  to  39°. 
Beyond  the  optimum  the  rate  rapidly  decreases,  cessation  of 
movement  being  reached,  in  the  case  of  Elodea,  in  3.7°,  in 
Vallisneria  in  6.2°,  in  Chara  in  8.4°  beyond  the  optimum. 
The  curves  exhibited  in  Fig.  68  are  characteristic  of  other 
vital  functions  besides  motion,  and  illustrate  this  general  law, 
that  the  optimum  temperature  for  the  vital  activities  lies 
much  nearer  to  the  maximum  vital  temperature  than  to  the 
minimum. 

After  having  seen  that  the  rate  of  flow  of  protoplasm  is 
dependent  upon  temperature,  we  should  expect  to  find,  as  we 
do,  that  that  other  form  of  protoplasmic  motion,  cilia  vibration, 
would  be  likewise  dependent.  Some  quantitative  data  con- 
cerning relation  of  temperature  and  rate  of  vibration  were 
gained  as  early  as  1858  by  CALLIBUKCES.  He  placed  a  bit  of 
ciliated  membrane  from  the  frog's  oesophagus  in  a  moist  cham- 
ber, and  in  contact  with  the  cilia  he  laid  a  small  glass  cylinder, 
horizontally  supported,  and  provided  with  a  dial  by  which  its 
revolutions  could  be  counted.  He  found  that  the  mean  time 
for  a  revolution  was,  — 

at  12°  to  19°  C 22  minutes,  3  seconds ; 

at  28°  C.  ....       3  minutes,  7  seconds ; 

thus,  in  increasing  the  temperature  from  15°  to  28°  C.,  the  rate 
of  vibration  is  increased  sevenfold. 

Essentially  similar  results  were  obtained,  through  the  use  of 
new  methods,  by  ROTH  ('66,  pp.  185-189),  upon  the  ciliated 
epithelium  of  the  frog's  uterus,  rabbit's  trachea,  and  gill  of 
Anodonta,  and  by  EXGELMAXX  ('68,  pp.  381-384 ;  443,  444 ; 
454,  455  ;  and  '77),  upon  the  frog's  oesophagus.  The  simplest 
of  these  methods  was  to  determine  the  rate  of  the  transportation 
of  fine  particles  over  the  surface  of  the  tissue.  The  result  of 
these  studies  showed  that  the  optimum  temperature  for  the 


LIBR, 

OF  THK 


228 


HEAT   AND   PROTOPLASM 


[Cn.  VIII 


movements,  of  Vertebrate  cilia  lies  between  35°  and  40°  C., 
and  that  a  gradual  elevation  of  temperature  to  this  point  is 
accompanied  by  gradual  increase  in  the  rapidity  of  the  stroke, 
the  law  of  which  is  exhibited  in  the  curves  shown  in  Figs.  69 
and  70. 

This  variation  in  rate  and  regularity  of  cilia  movement  with 
change  in  heat  is  marked  in  Infusoria,  as  ROSSBACH  ('72,  p.  312) 


70 


50 


10 


\ 


0' 


10' 


20' 


FIG.  69.  —  Curves  showing  relation  between  temperature  (curve  TT)  and  rapidity 
of  movement  of  the  cilia  of  the  mouth  and  oesophagus  of  the  frog.  The  abscissae 
give,  in  minutes,  the  lapse  of  time  from  the  beginning  of  the  experiment.  The 
ordinates  give,  for  the  temperature  curve,  the  degrees  Centigrade,  and,  for  the 
other  curve,  the  corresponding  number  of  units  of  motor  activity  for  the  imme- 
diately preceding  2  minutes  as  registered  by  ENGELMANN'S  apparatus.  (From 
ENGELMANN,  '77.) 


and  SCHURMAYEK  ('90,  pp.  411,  412)  have  shown.  The  lower 
the  temperature  falls  below  15°  C.,  the  slower  the  locomotion, 
almost  ceasing  at  +4°.  Upon  raising  the  temperature  above 
15°,  motion  quickens,  until,  between  25°  and  30°,  motion 
reaches  a  maximum,  the  Ciliata  shooting  back  and  forth  with 
the  quickness  of  an  arrow.  Between  30°  and  35°,  the  move- 
ments become  still  more  violent,  and  take  on  a  new  character. 
They  are  no  longer  coordinated.  Towards  40°,  the  progres- 


§2] 


EFFECT  OX  GENERAL  FUXCTIOXS 


229 


sive  movement  becomes  slower,  and  finally  ceases,  while  the 
rotation  continues,  but  in  ever  diminishing  rapidity.  A  new 
axis  of  rotation  is  assumed,  running  lengthwise  and  obliquely, 
or  running  transversely,  in  the  short  axis  of  the  body.  Finally, 
somewhere  between  38°  and  40°,  motion  ceases.  Thus,  the 
optimum  temperature  for  the  activities  of  the  protoplasm  lies 
at  about  30°  C.,  and  the  maximum  temperature  is  perhaps  10° 
higher. 

The  experiments  upon  plant  protoplasm,  amoeboid  organisms, 
and  ciliated  cells  thus  agree  in  demonstrating  a  close  relation  be- 


so 


\ 


\ 


\ 


o' 


10' 


20' 


30 


40' 


FIG.  70.  —  A  set  of  curves  having  the  same  meaning  as  those  of  Fig.  69.  In  this  case, 
however,  the  temperature  first  falls  and  then  rises,  instead  of  rising  first  and  then 
falling.  (From  EXGELMAXX,  '77.) 

tween  temperature  and  protoplasmic  movement.  This  relation 
is  such  that,  as  the  temperature  is  elevated  above  the  freezing 
point  of  water,  the  movements  regularly  increase,  and  reach 
their  greatest  activity  at  about  the  temperature  of  slow-running 
waters  in  the  midst  of  summer,  namely,  about  25°  to  30°  C.* 

*  The  maximum  temperature  .attained  by  bodies  of  ordinary  water  inhabited 
by  organisms  seems  to  be  close  to  the  position  of  the  optimum  temperature  of 
organisms.  Yet,  temperature  data  concerning  the  waters  from  which  the  organ- 


230  HEAT   AND   PROTOPLASM  [Cn.  VIII 

Above  this  temperature,  the  rate  of  protoplasmic  movement 
rapidly  decreases. 

That  temperature  influences  the  irritability  of  protoplasm 
is  demonstrated  by  many  facts.  Thus,  STRASBUKGER  ('78,  p. 
611)  found  that,  at  a  high  temperature,  the  light  attunement 
of  swarm-spores  changes.  For  example,  swarms  of  Haematococ- 
cus  and  Ulothrix,  which  are  —  phototactic,  move  at  30°  C.  from 
the  -  -  to  the  -+-  side  of  the  drop.  LOEB  ('90,  p.  43)  has 
found  that  Prothesia  larvse  do  not  respond  to  light  at  a  tem- 
perature below  -f- 13°  C.  Similarly,  in  respect  to  geotaxis, 
SCHWABZ  ('84,  p.  69)  found  that  Euglena  did  not  respond 
at  below  5°  to  6°  C.  So,  too,  CAMPBELL  ('88,  p.  130)  has 
shown  that  the  response  of  muscles  to  electric  stimulus  varies 
with  the  temperature.  Thus,  with  the  neck  muscles  of  the 
tortoise  at  — 


NUMBER  OF  SHOCKS  PER  SECOND  REQUIRED 
TEMPERATURE. 


4°C. 

9°C. 
21°  C. 

28°  C. 


1 
5 

25 
34 


isms  of  the  experiment  have  been  taken  are,  unfortunately,  rarely  given  in 
experiments  on  heat.  From  observations  made  by  the  Massachusetts  State 
Board  of  Health  (Report  on  Water  Supply  and  Sewage,  1890,  Part  I,  p.  660),  it 
appears  that  the  various  ponds  and  reservoirs  in  the  state,  having  a  depth  varying 
from  19  to  5  metres,  had  a  mean  August  (maximum)  temperature  ranging  (in 
the  different  ponds)  from  24°  to  21°  C.  Various  rivers,  mostly  not  of  mountain 
origin,  had,  in  1887,  a  mean  July  (maximum)  temperature,  varying  (in  different 
cases)  from  26.5°  to  24°  C.  Even  in  those  ponds  and  streams  in  which  the 
surface  temperature  is  over  25°,  a  lower  temperature  can  be  found  below  the 
surface.  Thus,  from  the  report  referred  to,  it  appears  that,  while  at  3.3  metres 
below  the  surface  we  have  nearly  the  surface  temperature,  at  6.6  metres  below 
the  surface,  we  find  a  decrease  of  3°  to  10°,  and  at  10  metres  a  decrease  of 
from  9°  to  17°  below  the  surface  temperature  in  different  ponds.  As  for  the  sea, 
the  highest  recorded  surface  temperature  is  about  32°  C.  (Ked  Sea,  Gulf  of 
Mexico.)  See  A.  AGASSIZ,  "Three  Cruises  of  the  Blake,"  Bull.  Mus.  Comp. 
Zool.,  XIV,  p.  301.  It  would  be  a  valuable  piece  of  work  to  determine  the 
maximum  summer  temperature  attained  by  the  waters  of  shallow  ponds,  pools, 
and  marshes  inhabited  by  organisms. 


§3]  TEMPERATURE-LIMITS  OF  LIFE  231 

This  shows  that  the  muscle  responds,  and  tends  to  return  to 
its  uncontractecl  condition  less  quickly  at  a  low  than  at  a  higher 
temperature.  In  general,  then,  protoplasm  is  more  responsive, 
the  closer  we  approach  its  optimum  temperature. 


§  3.     TEMPERATURE-LIMITS  OF  LIFE 

In  the  preceding  sections  we  have  seen  that,  as  the  tempera- 
ture is  raised  above  the  optimum,  or  as  it  approaches  0°  C., 
the  vital  activities  begin  to  diminish.  Finally,  we  meet  with  a 
higher  or  a  lower  limit,  at  which  all  movement  and  the  processes 
of  metabolism  cease.  This  point  may  be  called,  in  the  case  of 
the  higher  limit,  the  maximum,  and  in  the  case  of  the  lower 
limit,  the  minimum.  The  maximum  and  the  minimum  are  not 
points  of  death,  but  merely  of  cessation  of  activity,  lasting 
while  the  temperature  endures,  but  being  replaced  by  renewed 
activity  when  the  temperature  is  shifted  towards  the  optimum. 
This  quiescent,  or  latent,  condition  of  the  protoplasm  near 
the  vital  limits  of  temperature  may  be  called  temporary  rigor 
(German  "  Starre  ")  to  distinguish  it  from  death.  Death  occurs 
at  a  very  few  degrees  beyond  temporary  rigor. 

1.  Temporary  Rigor  and  Death  at  the  Higher  Limit  of  Tem- 
perature, Maximum  and  Ultramaximum.  (EXGELMANN,  '79, 
p.  358.)  —  The  occurrence,  at  a  high  temperature,  of  a  con- 
dition resembling  death,  except  that  the  organism  may  revive 
from  it,  seems  first  to  have  been  noticed  by  P.  DE  CANDOLLE 
('06,  p.  346).  He  found  that  a  Sensitive  plant,  kept  11  hours 
at  37°  C.,  lost  all  sensibility  to  touch,  and  did  not  close  with 
the  coming  on  of  night.  Maintained,  during  the  following 
day  and  night,  at  a  temperature  of  about  20°,  it  remained 
insensitive  during  that  period ;  but  on  the  succeeding  night 
it  closed  its  leaves,  and  on  the  following  day  had  regained  its 
sensitiveness  to  touch.  Thus,  the  high  temperature  of  37°  had 
produced  an  immotile  state  which  was  not  death,  since  it  was 
only  temporary.  It  may  be  called  the  state  of  temporary  heat- 
rigor. 

The  earliest  record  which  I  have  found  of  a  similar  observa- 
tion among  animals  is  that  of  PICKFORD  ('51).  He  states 
that,  at  a  high  temperature,  muscle  went  into  a  rigid  con- 


232  HEAT   AND  PROTOPLASM  [Cn.  VIII 

dition  ("  Scheintodtenstarre  ")  from  which  it  might  return  to 
a  normal  condition  of  sensitiveness.  Such  a  rigid  state  was 
brought  about  by  subjecting  a  decapitated  frog  in  water  to 
35°  R.  (43.8°  C.)  for  1  minute.  I  will  now  add  some  additional 
cases  of  production  of  temporary  heat-rigor  in  protoplasm  which 
I  have  found  in  the  literature. 

In  1863,  MAX  SCHULTZE  (pp.  33,  34)  found  temporary  heat-rigor  in 
Actinophrys,  which  retracts  its  pseudopodia  and  appears  as  a  lifeless  mass 
at  35°  to  38°,  but  is  not  killed  until  43°  is  reached.  In  the  same  year  SACHS 
('63,  p.  453)  repeated  more  fully  the  experiments  of  P.  DE  CANDOLLE  on 
Mimosa  pudica.  He  found  that  a  temperature  of  30°  C.  for  3  hours  did  not 
produce  rigor.  A  temperature  of  40°  for  1  hour  produced  loss  of  sensibility 
during  20  minutes.  Raised  slowly  even  to  50°,  sensibility  was  only  tempo- 
rarily lost,  but  52°  proved  fatal.  Immersed  in  water,  heat-rigor  occurred 
at  a  temperature  5°  to  10°  lower.  SACHS  clearly  distinguishes  a  "voriiber- 
gehende  Warmestarre  "  from  death. 

KUHNE  ('64,  pp.  45,  67,  87,  103)  drew  a  sharp  contrast  between  the 
rigidity  of  death,  which  he  calls  "  Warmestarre,"  and  the  transitory  immobile 
condition  or  "  Warinetetanus."  He  found  this  latter  condition  to  occur  in 
Amoeba  subjected  to  35°  for  1  minute,  in  Actinophrys  subjected  to  35°-40° 
for  several  minutes,  in  motile  Myxomycetes  (Didymium  serpula)  subjected 
to  30°  for  5  minutes,  in  Tradescantia  stamen  hairs  at  over  45°,  when  gradu- 
ally brought  to  that  temperature.  In  all  cases  there  is  such  a  relation 
between  temperature  and  time  of  subjection  that  the  greater  the  one  is  the 
less  need  be  the  other  in  order  to  produce  heat-rigor. 

Very  instructive  also  are  the  observations  of  HOFMEISTER  ('67,  pp.  54, 
55)  which  I  briefly  summarize :  Hairs  from  the  stem  and  leaf  of  Ecbalium 
ageste  showing  lively  movement  were  gradually  raised  from  16°-17°  C.  to 
40°  C.  They  became  motionless  at  40°  C.  After  1  to  2  hours,  movement 
returned,  and  was  very  violent.  Cooled  and  raised  again  to  45°  C.,  the  proto- 
plasm was  motionless  at  first,  but  after  17  minutes  movements  recurred  but 
were  not  rapid.  Put  again  into  47.5°  (after  first  cooling)  heat-rigor  occurred 
in  5  minutes,  but  upon  cooling,  movements  return. 

Very  similar  experiences  have  befallen  subsequent  investiga- 
tions which  unite  in  supporting  the  conclusion  that  at  a  certain 
temperature,  slightly  below  the  death  point,  protoplasm  becomes 
immobile,  but  retains  the  capacity  for  subsequent  reacquisition 
of  movement  upon  lowering  the  temperature. 

Finally,  studies  upon  i;  uscle,  especially  those  of  CHMULE- 
VITCH  ('69),  SAMKOWY  ('74),  MORIGGIA  ('91),  GOTSCHLICH 
('93),  and  others,  have  shown  that  as  the  temperature  is  ele- 
vated up  to  about  30°  C.,  the  muscle  contracts  more  and  more, 


§3]  TEMPERATURE-LIMITS  OF   LIFE  233 

lengthening  again  as  the  temperature  falls.  If,  however  (GoT- 
SCHLICH),  the  temperature  is  raised  in  about  60  seconds  to  38° 
and  then  lowered,  the  elongation  of  the  muscle  takes  place  only 
very  slowly.  This  is  the  condition  of  "thermische  Dauerverk- 
urzung,"  and  is  probably  the  same  as  the  condition  of  tempo- 
rary heat-rigor  of  SACHS.  When,  however,  the  temperature 
is  raised  rapidly  to  45°  to  50°  (or  slowly  to  35°),  death-rigor 
appears,  accompanied  by  a  coagulation  of  the  protoplasm 
which  renders  the  whole  mass  opaque  and  permanently  con- 
tracted. The  rapidly  replaced  contraction  accompanying  ele- 
vation to  about  30°,  the  slowly  obliterated  contraction  of  38°, 
and  the  permanent  contraction  of  45°  are  then  three  stages  in 
a  series  of  effects  of  heat  on  muscle. 

If  now,  contraction,  heat-rigor,  and  death-rigor  are  merely 
three  stages  in  a  series  of  effects  of  increasing  temperature, 
they  probably  have  related  immediate  causes.  Heat-rigor  is 
certainly  a  condition  of  tetanus,  but  the  fact  that  the  proto- 
plasm in  this  condition  is  not  sensitive  and  cannot  quickly 
return  to  the  relaxed  condition  indicates  that  some  of  those 
changes  that  produce  death-rigor  have  already  occurred,  but 
not  to  such  an  extent  that  the  organism  cannot  recover  from 
them.  As  GOTSCHLICH  says  ('93,  p.  154),  "Die  thermische 
Dauerverkurzung  ist  also  eine  qualitative  unvollendete  Starre" 
(i.e.  death-rigor).  From  this  point  of  view  there  is  no  exact 
point  at  which  heat-rigor  occurs,  since  the  period  of  persisting 
rigidity  varies  in  extent  from  0  to  many  hours,  and  thus  passes 
by  almost  imperceptible  gradations  from  a  contraction  in  re- 
sponse to  heat  on  the  one  hand  to  death-rigor  on  the  other. 
The  muscle  increases  in  sensitiveness  as  the  temperature  rises 
to  the  optimum,  just  as  the  movements  of  plasma  in  Chara  do. 
Beyond  the  optimum,  sensitiveness  diminishes,  and  this  leads 
to  a  condition  of  heat-rigor  which  becomes  the  more  pronounced 
the  higher  the  temperature,  until,  through  completed  coagula- 
tion, death  occurs. 

We  must  now  consider  this  point  at  which  death  occurs 
from  heat ;  and,  as  an  introduction  to  this  discussion,  we 
may  tabulate  the  results  of  experiments  by  numerous  ob- 
servers who  have  attempted  to  determine  the  ultramaximum 
temperature. 


234 


HEAT  AND  PROTOPLASM 


[On.  VIII 


TABLE  XIX 

EESDLTS  OF  EXPERIMENTS  TO  DETERMINE  THE  ULTRAMAXIMUM  TEMPERATURE 
OF  ORGANISMS  IN  WATER,  OR  THE  TEMPERATURE  AT  JUST  ABOVE  WHICH 
ORGANISMS  REARED  UNDER  NORMAL  CONDITIONS  WILL,  DIE 


SPECIES. 

MAXIMUM 
TEMPERATURE. 

CONDITIONS  OP 
EXPERIMENT. 

AUTHORITY. 

Cryptogams. 

45°  C 

Maximum  temperature 

COHN     '77    p.  <?53- 

Yeast                            .  .  . 

53° 

of  growth  in  liquid 
Moist  •   average  max. 

'94,  p.  150 

SCHUTZENBERGER, 

Oscillatoriae           

45°         1 

'79,  p.  162 

42° 

Spirogyra      j 

Death  point 

DE  VRIES,  '70,  p. 

(Edogonium  j 
Hydrodictyon        

46° 

388 

45°  to  60° 

SACHS  '64  p  5 

Nitella  flexilis    

45° 

Gradually  raised 

DUTROCHET,  '37,  p. 

Funaria  hygrometrica  .  . 

Marchantia  polymorpha  \ 
Lunularia  vulgaris 

Phanerogams. 
Vallisneria  spiralis  .... 
Ceratophyllum  demersum 

Various  plant  cells  .... 

Protozoa. 
-'Kthulium  sept 

43° 
46° 

45°  to  50° 
45°  to  50° 

47°  to  48° 
40° 

Gradually  raised       ~\ 
Suddenly   immersed  \ 
for  10  minutes       J 
Died    (suddenly    sub- 
jected) 

777 
DE  VRIES,  '70,  p. 
388 
«               « 

SACHS,  '64,  p.  5 

SCHULTZE,   '63,  p. 

48 

KUHNE   '64  p  87 

Amoeba 

40°  to  45° 

2  minutes 

Actinophrys  

42° 

Death  point    Activity 

SCHULTZE    '63    p 

Miliolidae    

43° 

lost  at  38° 
Death  point 

34 
SCHULTZE    '63    p 

Various    Flagellata    and 
swarm-spores  

Various  Infusoria 

40°  to  60° 

45° 

45°  to  60°  most  usual. 
Heat-rigor     usually 
occurs  between  40°  to 
50°  and  is  lower  for 
marine  than  for  f  .  w. 
species.    These  tem- 
peratures    for    the 
motile  stage 

38 

BUTSCHLI,     '84,     p. 

860  ;    STRASBUR- 
GER,  '78,  p.  611; 
DALLINGER,  '80, 
p.  10 

short  time 

p.  412 

TEMPERATURE-LIMITS  OF  LIFE 


•  UK 
235 


SPECIES. 

MAXIMUM 
TEMPERATURE. 

CONDITIONS 
OF  EXPERIMENTS. 

AUTHORITY. 

Paramecium  

42°  to  46°  C. 

Gradually  subjected 

MENDELSSOHN,  '95 

Stentor 

44°  to  50° 

Heat-rigor  point  tem- 

p. 19 
DWENPORT      and 

Vorticellidae  

41°  to  42° 

perature  raised  grad- 
ually.   From  a  pool 
kept  warm  by  boiler 
waste 

CASTLE,    '95,    p. 
229 

SCHULTZE,    '63,    p. 

Cuelenterata. 

Actinia             . 

38° 

Gradually    raised    (1 

49 
FRENZEL,    '85     p 

Beroe  ovatus            .      .  . 

40° 

hour) 
Death  point,  suddenly 

464 
DE  VARIGNY,    '87 

Mollusca. 
Various  ^Mollusca  

30°  to  40° 

subjected 
Suddenly  immersed 

p.  63 
FRENZEL,    '85,    p. 

Pleurobranchsea    
Aplysia 

33° 
33° 

Temp,  gradually  raised 
Died  in  3  hours 

461^66 
«              « 

<«               « 

Eledone   

35° 

Died 

«               « 

Young  squids              • 

37° 

Heat-rigor  •  died  at  41° 

BERT  '67  p.  135 

Vermes. 
Turbellaria   

44.5° 

Death  point 

SCHULTZE,  '63,   p. 

Anguillulidae   

445° 

..     ..          I 

49 
SPALLANZANI, 
1787,  Tom.  I.,  p.  56 

Rotifera       1 

45°  to  48° 

1 

Moist 

SCHULTZE,   '63,   p. 
49 
DOYERE,  '42,  p.  29 

Tardigrada  J 
Diopatra 

98° 
40° 

Dried 
Suddenly     immersed 

BROCA,  '61,  p.  44-46 
FREXZEL    '85,  pp^ 

Terebella    

27°  to  30° 

died  quickly  ;  at  30° 
lived  indefinitely 
Suddenly     heated  ; 

461^65 
«                « 

Na'ididfe 

44  5° 

slowly  warmed,  re- 
sisted 30° 

SCHULTZE,  '63,  p. 

"  Bloodsucker  " 

44° 

Death  point 

49 
SPALLANZANI, 

Crustacea. 
Daphnia  sima  

33.5° 

Suddenly  subjected 

1777,  Tom.  I,  p.  56 

PLATEAU,'72,p.316 

Cyclops  quadricornis  1 
Cypris  f  usca 
Gammarus  roselii  
Asellus  aquaticus  

36° 

36° 
43.5° 

«              « 

"  317 

"  316 
"  316 

236 


HEAT  AND  PROTOPLASM 


[Cn.  VIII 


SPECIES. 

MAXIMUM 
TEMPERATURE. 

CONDITIONS  OF 
EXPERIMENT. 

AUTHORITY. 

26°  C. 

Died  in  2  hours  (sud- 

FRENZEL    '85     p 

Scyllaris  

30° 

denly  subjected) 
Died  in  1  hour  (sud- 

463 

«               « 

Pagurus  prideauxii  .... 
Dromia  vulgaris    
Pisa  gibbosa  .'  .  • 

36° 
38° 
36° 

denly  subjected) 

DE  VARIGNY   '87a 

Portunus  puber     .         .  . 

^ 
34° 

Death  point 

p  173 

Carcinus  sp  

38° 

Grapsus  sp             

38°        J 

Arachnida. 
Argyroneta  aquatica  .  .  . 

Hydrachna  cruenta  .... 

Insecta. 
Podura 

38.5° 
46.2° 

27° 

Suddenly  subjected 
Submerged  (?) 

Suddenly    subjected  ' 

PLATEAU,    '72,    p. 
316 
«<              « 

NICOLET  '42  p  11 

Agabus  bipustulatus  .  .  . 
Hydaticus  transversalis  . 
Culex  pipiens,  larva  .  .  . 
Hydrophilus  caraboides  . 
Hydroporus  dorsalis  .  .  . 
Nepa  cinerea 
Notonecta  glauca     r  •  •  • 
Cloe  diptera,  larva  J 
Musca  vom.  (?)  
Musca  vom.,  larva  .... 
Musca  vom.,  pupa   .... 
Silk  worm  larva    

38°        1 
39° 
40° 

42° 
42° 

44°  to  45° 

j 
37.5°     ' 
42.5° 
43.7° 
42.5° 

died  slowly.    At  36° 
died  at  once 

Death  point 
Death  point 

PLATEAU,    '72,   p. 
316 

SPALLANZANI,  1787, 
Tom  I  pp  56-58 

"  Butterfly  "  larva  .... 
Culex  larva 

42.5° 

43  7° 

Echinodermata. 
Antedon  

30° 

FRENZEL    '85    pp 

Holothuria    ... 

30°  to  40° 

denly  subjected) 

460-463 

«               « 

Vertebrata. 
Many  fresh-water  fishes  . 

Fish    

40° 
f       36° 
j        330 

(suddenly  subjected) 

Survived  only  a  few 
seconds 
In  pond  out  of  doors. 

EDWARDS,    '24,    p. 
114 
KNAUTHE,  '95,   p. 
752 
BERT   '76  p  169 

27°  to  38° 

gradually 

DAVY,  '63,  p.  125 

TEMPERATURE-LIMITS  OF   LIFE 


237 


SPECIES. 

MAXIMUM 
TEMPERATURE. 

CONDITIONS  OF 
EXPERIMENT. 

ACTHO.RITY. 

Hippocampus  

30°  C. 

Lived  half  an  hour 

FREXZEL     '85     p 

Salamander 

44° 

Death  point 

462 

SP  A.LLA'VZ  A.NI 

Fro0"  .                  

40°  to  42° 

Suddenly  subjected  in 

1787,  Tom.  I,  p.  56 
EDWARDS     >f)4    p 

Frog,  adult  (summer)  .  . 
Frog,  adult   

42°  to  43° 
43.8° 

water  ;  death  at  once 
Death-rigor  in  7  to  14 
minutes 

374 

MORIGGIA,     '91,    p. 

385 
SPALL  A.XZ  \vi 

41° 

Raised  in  from  5  to  10 

1787,  p.  55 
See  p  253 

Kabbit  1 

44°  to  45° 

minutes 
Death     point     when 

OBERNIER,   '66,  p. 
22 

Dog       I 
Man 

45° 

convulsions  at  42° 
In  water  *  giddiness  in 

EDWARDS     '^4    p 

Human  spermatozoa  .  .  . 
Vertebrate  muscle  .... 
Vertebrate  muscle  (frog) 

50° 
40°  to  50° 

[  45°  to  50° 

|       35° 

a  few  seconds 
Died  in  10  minutes 

Raised  in  30  seconds 
Raised  in  18  minutes 

374 
MANTEGAZZA,  '66, 
p.  186 
KUHNE,     '59,    pp. 
784-804 
GOTSCHLICH,     '93, 
p.  123 

The  determinations  given  in  the  above  table  may  be  compared 
only  with  caution,  for  diverse  conditions  give  results  which 
cannot  be  directly  correlated.  Thus  individuals  of  the  same 
species,  but  reared  under  diverse  environment,  have  a  different 
resistance  period  to  heat.  The  lethal  temperature  varies  accord- 
ing as  the  organisms  are  suddenly  or  gradually  subjected  to  the 
high  temperature.  Also,  the  individuals  of  the  same  species 
will  die  at  different  temperatures  according  as  they  are  rap- 
idly subjected  to  the  high  temperature  or  gradually  accus- 
tomed to  it,  and,  as  we  have  seen,  a  lower  temperature,  long 
continued,  often  produces  the  same  result  as  a  higher  tempera- 
ture during  a  brief  period.  Finally,  too  little  care  has  been 
exercised  in  most  cases  to  determine  the  temperature  of  the 
water  immediately  upon,  and  a  few  minutes  after,  placing  the 
animals  in  it,  —  an  operation  which  lowers  the  temperature 
of  the  water.  In  the  experiments  cited,  unless  otherwise 
stated,  the  conditions  were  gradual  subjection  continued  for 
a  short  time  only.  The  quality  of  the  water  in  which  the 


238  HEAT  AND   PROTOPLASM  [On.  VIII 

experiments  were  carried  on  is  supposed  to  be,  except  for  its 
temperature,  normal  for  the  species.  Summarizing  the  table, 
we  find  that  the  Protista  have  the  highest  maximum  tempera- 
ture of  any  group,  it  being  in  extreme  cases  about  60°  for  active 
organisms,  but  generally  between  40°  and  45°.  Among  the 
Metazoa,  the  highest  maxima  recorded  (excepting  Rotifera  and 
Tardigrada)  are  44°  to  45°  for  Turbellaria,  Anguillula,  Naididse, 
Nepa  (water-scorpion),  Notonecta  (water-boatman),  Cloe  larva, 
Salamander,  and  mammals.  A  water-mite  (Hydrachna)  is 
said  to  have  withstood  up  to  46.2°,  and  some  vertebrate  tissues 
resist  up  to  50°.  For  the  great  majority  of  Metazoa,  the  maxi- 
mum temperature  lies  below  45°  and,  in  the  case  of  marine 
species,  below  40°.  The  low  maximum  temperature  of  marine 
species  is  probably  due  to  the  low  maximum  temperature  of 
the  sea  as  compared  with  ponds.  We  may  consequently  con- 
clude from  the  foregoing  that  the  maximum  temperature  for 
protoplasm  lies  generally  between  35°  and  50°,  the  lower  limit 
being  characteristic  of  organisms  living  in  a  medium  of  low 
temperature  (the  sea),  the  latter,  of  organisms  reared  in  warm 
pools  or  of  organs  (vertebrate  muscle)  in  a  body  kept  at  a  high 
temperature. 

The  question  now  arises,  what  is  the  cause  of  the  death  of 
protoplasm  at  high  temperatures?  To  get  some  insight  into 
this  matter,  let  us  examine  the  phenomena  accompanying  death 
of  protoplasm  from  overheating.  KUHNE  ('64,  p.  44)  thus 
describes  the  appearance  of  an  Amoeba  subjected  for  a  moment 
to  a  fatal  temperature  (45°).  The  structure  is  entirely  altered 
since  it  has  become  transformed  into  a  mass  of  knobbed,  opal- 
escent, solid  lumps,  which,  even  in  transferring  to  the  slide, 
become  easily  broken  apart.  This  appearance  is  clearly  due 
to  a  coagulation  of  the  protoplasm.  A  similar  coagulation 
takes  place  in  Actinophrys  eichhornii  (KtJHNE,  '64,  p.  67)  at 
45°.  "  The  sphere  shrinks  into  a  flat,  hardly  transparent,  cake, 
no  longer  reacts  to  the  strongest  induction  shocks,  and  breaks 
up  after  24  hours  into  a  heap  of  small  granules  and  irregular 
pieces."  Likewise,  in  muscles  a  change  is  produced  by  heat 
which  is  evidently  a  kind  of  coagulation.  A  coagulation  then 
seems  to  be  the  immediate  cause  of  death  at  high  temperatures. 

But  just  what  is  the  component  of   protoplasm  which  co- 


§3]  TEMPERATURE-LIMITS  OF   LIFE  239 

agulates  at  the  death  point  of  organisms?  As  KUBGSTE  ("64, 
p.  1)  pointed  out,  it  cannot  be  ordinary  egg  albumen ;  for, 
excepting  the  contractile  substance,  we  know  of  no  native 
albumen  which  coagulates  between  35°  and  50°  C.  It  was 
KUHNE'S  great  service  to  show  that  there  is  a  substance  which 
can  be  pressed  out  of  frozen,  triturated,  and  then  thawed 
muscle,  which  becomes  quickly  opalescent  at  40°,  through  the 
separation  of  the  muscle  plasma  into  myosin  and  a  serum. 
This  serum,  in  turn,  contains  an  albuminoid  which  coagulates 
at  47°  (DEMANT,  '79  and  '80).  Now,  since  there  are  proteids 
in  muscle  which  coagulate  at  about  the  point  at  which  muscle 
goes  into  permanent  heat-rigor,  and  since  these  proteids  can 
no  longer  be  squeezed  out  of  rigid  muscles,  the  conclusion 
seems  justified  that  permanent  heat-rigor  in  muscle  is  due  to 
the  coagulation  of  these  proteids. 

Related,  easily  coagulable  proteids  occur  in  widely  dissimilar 
organisms.  For  example,  myosin  has  been  found  in  vegetable 
protoplasm  (\VEYL,  '77,  p.  96),  and  HALLIBURTON  ('88)  has 
described  a  globulin  from  blood  corpuscles  which  coagulates 
at  48°  to  50°.  Their  distribution  in  protoplasm  is,  therefore, 
probably  general,  and  so  we  are  justified  in  concluding  that  the 
death  of  protoplasm  by  heat  is,  in  general,  the  result  of  the 
coagulation  of  a  proteid  (globulin).  Death  occurs  because 
the  vital  machinery  has  been  broken  down.* 

2.  Temporary  Rigor  and  Death  at  the  Lower  Limit  of  Tem- 
perature, Minimum  and  Ultraminimum.  —  Whilst  towards  the 
upper  limit  of  ordinary  terrestrial  temperatures  (35°  to  40°  C.) 
molecular  changes  in  organic  compounds  are  hastened,  towards 
the  lower  limits  (—40°  to  —  50°)  molecular  changes  are  slow, 
being  principally  confined  to  the  transformation  from  the  liquid 
or  gaseous  to  the  solid  or  liquid  condition.  This  transforma- 
tion does  occur  in  the  water  of  protoplasm,  but  the  colloids, 

*  At  this  place  reference  may  be  made  to  the  fact  that  protoplasm  subjected 
to  a  high  temperature  sometimes  breaks  to  pieces  with  the  suddenness  and  com- 
pleteness of  an  explosion.  Thus  STRASBURGER  ('78,  p.  611)  found  that  Chilo- 
monas  curvata  was  uniformly  killed  at  45°  C.  by  the  explosion  of  the  body,  and 
Dr.  W.  E.  CASTLE  tells  me  that  he  has  observed  the  same  phenomenon  under 
like  conditions  in  Stentor.  An  investigation  of  this  profound  change  in  pro- 
toplasm would  be  sure  to  throw  valuable  light  upon  the  nature  of  the  living 
.substance. 


240  HEAT  AND   PROTOPLASM  [Cn.  VIII 

which  constitute  the  living  part,  are  not  modified  by  even  the 
lowest  of  the  terrestrial  temperatures,  except  that  the  molecular 
changes  which  they  undergo  are  very  slow.  This  being  true, 
protoplasm  which  contains  no  water,  or  very  little,  ought  not  to 
be  changed  by  low  temperatures,  —  that  is  to  say,  the  machine 
will  not  be  injured. 

With  the  activities  of  the  machine  —  with  the  vital  processes 
—  it  is,  however,  quite  different.  They  are  essentially  chemical 
processes,  and  hence  we  should  expect  them  to  be  diminished 
at  a  low  temperature.  If,  as  PICTET  ('93)  maintains  from  an 
extensive  and  highly  important  series  of  experiments,  no  chemi- 
cal processes  take  place  at  temperatures  below  —  100°  C.,  then 
protoplasm  ought  to  exhibit  no  vital  processes  at  this  tempera- 
ture, and,  indeed,  experience  shows  that,  as  we  have  already 
seen,  as  the  temperature  is  lowered  below  the  optimum,  all 
manifestations  of  activity  diminish.  It  is  clear  that  at  a  certain 
point  they  must  entirely  cease.  And  at  that  point  deathr 
following  the  usual  definition  of  the  word,  would  ensue. 

But  does  the  cessation  of  the  vital  processes,  without  injury 
to  the  mechanism,  necessarily  preclude  the  possibility  of  a 
return  to  activity  ?  Let  us  examine  the  experimental  evidence 
on  this  point.  SCHUMACHER  ('74,  p.  179)  subjected  yeast  to 
cold  and  found  that,  at  the  lowest  temperature  produced 
(—  113.7°),  the  yeast  cells  were  not  completely  killed.  More 
recently,  PICTET  ('93%  cf .  also  C.  DE  CANDOLLE,  '84)  has  sub- 
mitted various  dry  seeds  and  spores  of  bacteria  to  a  temperature 
of  nearly  —  200°,  at  which  temperature  the  atmosphere  becomes 
liquefied,  but  without  fatal  effects.  Other  results  were  still 
more  remarkable :  vibratile  cilia  from  the  mouth  of  the  frog 
were  cooled  to  —  90°,  and  recovered  their  movement  upon 
raising  the  temperature.  Some  Rotifera  and  Infusoria  were 
frozen  in  their  native  water  at  —  60°,  and  kept  at  that  tem- 
perature, apparently,  for  nearly  24  hours.  Most  have  subse- 
quently regained  their  activity.  Eggs  of  the  frog,  lowered 
slowly  to  —  60°,  can  revive.  Eggs  of  the  silk-worm  can  resist 
to  —40°.  Other  experiments  of  PICTET*  will  be  referred  to 

*  This  general  criticism  of  PICTET' s  paper  is,  I  believe,  valid.  He  does  not 
give  us  data  enough  upon  time  of  subjection  to  the  low  temperature,  time  em- 
ployed in  reducing  the  temperature,  and  other  details.  Thus,  concerning  his 


§  3]  TEMPERATURE-LIMITS  OF  LIFE  241 

later.  As  a  result  of  these  and  others'  investigations  we  may 
conclude :  Protoplasm  may  under  certain  circumstances,  of 
which  one  of  the  most  important  is  the  absence  of  water,  resist, 
uninjured,  the  lowest  temperatures.  TJiere  is  no  fatal  minimum 
temperature  for  dry  protoplasm. 

We  must  now  turn  our  attention  to  those  cases  in  which  the 
phenomena  of  cessation  of  activity  or  death  appear,  and  seek 
to  determine  their  causes ;  and  first  concerning  temporary 
cold-rigor.  We  have  already  seen  that  as  the  temperature  is 
lowered,  the  rate  of  metabolic  processes  and  protoplasmic 
movements  is  lowered.  What  happens  at  the  lower  limit  of 
activity,  and  where  does  this  lie?  The  chlorophyll  granules 
of  Vallesneria  move  (according  to  VELTEX)  only  about  1  mm. 
per  minute  at  1°  C.  and  not  at  all  at  0°;  the  rotation  of  Nitella 
ceases  (\AGELI,  '60,  p.  77)  at  0°C.;  in  Tradescantia  hairs, 
movement  is  wholly  arrested  on  freezing  the  cell  sap  (KtJHXE, 
'64,  p.  100,  and  DEMOOR,  '94,  p.  194).  Even  in  seeds  and 
bacteria,  which  are  not  killed  by  the  lowest  temperatures,  all 
vital  activities  have  probably  ceased  at  0°,  for  DE  CANDOLLE 
('65)  found  that  in  only  one  species  out  of  ten  could  he  get  a 
seed  kept  at  0°  to  germinate,  and  even  then  germination  was  so 
retarded  that  it  took  from  11  to  17  days  as  opposed  to  4  days 
at  5.7°.  Likewise,  bacteria  do  not  multiply  below  +5°  to 
-f- 10°  (BOXARDI  and  GEROSA,  '89).  Among  animals,  KTJHNE 
('64,  p.  46)  found  Amoeba  cooled  to  near  0°  almost  motionless. 
PURKIXJE  and  VALENTIN  ('35)  first  noticed  that  the  ciliated 

experiments  on  Scolopendra,  lie  merely  says  :  "I  have  frozen  to  —  40°  three 
Scolopendras  which  perfectly  resisted  the  treatment  and  lived  after  thawing  out. 
Submitted  to  —  50°,  they  have  also  resisted.  Frozen  a  third  time  to  —  90°,  they 
are  all  three  dead."  Now,  in  the  absence  of  further  data,  it  is  quite  possible 
that  the  heat  of  metabolism  kept  the  internal  body  temperature  considerably 
above  that  of  the  chamber,  the  thick  cuticula  preventing  rapid  loss  of  heat,  very 
much  as  a  man's  clothing  enables  him  to  withstand  the  —  40°  of  an  arctic  winter. 
Another  experiment  of  PICTET'S  lends  greater  probability  to  this  explanation  of 
some  cases  of  great  resistance.  Three  snails  were  subjected  to  a  temperature  of 
from  —  110°  to  —  120°  during  several  days.  The  operculum  of  two  of  these  was 
not  intact,  so  that  it  did  not  close  the  orifice.  These  two  individuals  died ;  but 
the  third,  which  was  completely  sealed  up,  survived.  Those  which  were  not 
sufficiently  clad,  so  to  speak,  lost  so  much  internal  heat  that  their  internal  fluids 
were  frozen.  Of  course  this  criticism  cannot  apply  in  the  case  of  those  organ- 
isms mentioned  in  the  text  which  are  without  a  thick  cuticula. 


242  HEAT   AND   PROTOPLASM  [Cn.  VIII 

epithelium  of  the  frog  ceased  its  movements  at  0°.  Muscles 
of  the  frog  were  found  by  KUHNE  ('64,  p.  3)  to  become  at 
_  3°  to  —  7°  a  solid  lump  which  did  not,  however,  wholly  lack 
irritability.  The  evidence  of  all  these  cases  shows  that  activity 
nearly  ceases  in  protoplasm  at  or  near  0°  C. 

Another  effect  produced  on  protoplasm  by  cold  —  an  effect 
which  often  immediately  precedes  quiescence  —  is  violent  con- 
traction. This  has  been  repeatedly  observed.  The  protoplasm 
of  Tradescantia  hairs,  which  has  been  in  cold-rigor,  was  found 
by  KLJHNE  ('64,  p.  101)  to  lie  in  separated  rounded  drops  and 
lumps,  —  an  appearance  like  that  resulting  from  excessive  stimu- 
lation. The  rapid  freezing  of  muscle  gives  rise,  according  to 
HERMANN  ('71,  p.  189),  to  violent  contractions.  The  sciatic 
nerve  of  the  frog's  leg  when  cooled  to  —  4°  to  —  8°  causes  clonic 
contractions  of  the  muscle,  lasting  two  minutes.  (AFFAXA- 
SIEFF,  '65,  p.  678,  and  others.)  It  is  clear,  then,  that  cold  acts 
as  a  violent  stimulus  to  protoplasm. 

The  final  result  of  temporary  rigor  is  thus  clearly  brought 
about  by  the  cooperation  of  two  causes  :  (1)  the  diminution  in 
the  chemical  processes  upon  which  metabolism  and  movement 
depend,  and  (2)  the  directly  stimulating  effect  of  the  cold, 
which  acts  like  contact  or  excessive  heat.  Both  causes  work 
to  produce  a  quiescence  which  may  be  replaced  by  activity 
when  the  causes  are  withdrawn. 

The  fact  that  cold-rigor  usually  occurs  close  to  the  zero- 
point  indicates  that  the  activities  of  protoplasm  are  closely 
determined  by  the  fluid  state  of  water.  This  fact  is  not  to  be 
explained  on  the  ground  that  freezing  prohibits  all  chemical 
change  —  many  chemical  changes  take  place  below  the  freez- 
ing point  of  water,  but,  apparently,  few  of  those  which  are 
involved  in  metabolism.  Nor  is  the  rigor  due  to  the  change 
which  the  freezing  of  the  protoplasmic  fluids  brings,  because 
as  the  temperature  approaches  the  zero-point,  but  while  the 
water  is  still  perfectly  fluid,  metabolism  diminishes  ;  and  it 
diminishes  at  such  a  rate  as  to  cease  just  where  water  begins  to 
freeze.  The  critical  point  for  vital  activity  has  been  adjusted 
to  this  critical  point  of  water. 

So,  too,  the  composition  of  protoplasm  is  such  that  at  a  tem- 
perature, lying  below  the  normal  and  above  the  freezing  point 


§3]  TEMPERATURE-LIMITS  OF  LIFE  243 

of  water,  those  chemical  changes  rapidly  occur  which  we  desig- 
nate response  to  the  stimulus  of  cold.  This  composition  of 
protoplasm,  upon  which  cold  can  work  such  important  modifi- 
cations, is  a  quality  of  immense  importance  in  the  economy  of 
the  organism,  as  the  changes  of  each  autumn  testify. 

Below  the  point  of  temporary  cold-rigor  lies  that  of  death, 
if  death  point  there  be.  The  position  of  the  death  point  is, 
however,  very  diverse  in  different  organisms.  Part  of  the 
diversity  in  the  death  points  assigned  by  different  authors  is, 
however,  due  to  the  fact  that  in  the  methods  of  determining 
the  death  points  there  has  been  a  lack  of  uniformity. 

Five  elements  ought  always  to  be  regarded  in  experiments 
on  the  ultrarninimuin  temperature.  (1)  History  of  the  tem- 
perature conditions  in  which  the  individual  or  its  race  had 
lived  before  experimentation ;  (2)  rate  at  which  the  organ- 
ism has  been  cooled,  —  if  possible,  the  temperature  of  the 
organism  itself  rather  than  that  of  the  medium  ;  (3)  inten- 
sity of  cold  just  sufficient  to  kill ;  (4)  duration  of  applica- 
tion of  the  cold  and  the  kind  of  medium  in  which  the 
erganism  is  subjected  to  the  cold ;  *  and  (5)  the  rate  of 
thawing  out.f  These  elements  have  been  too  much  neg- 
lected in  the  past. 

I  shall  now  present  in  tabular  form  some  of  the  more 
reliable  determinations  of  the  death  point  of  organisms,  pref- 
acing with  the  caution  that  the  results  are  not  closely 
comparable. 

*  The  duration  of  application  and  intensity  of  the  fatal  cold  stand  in  an 
inverse  relation,  so  that  organisms  which  resist  a  temperature  —  A°  for  X  min- 
utes will  resist  a  lower  temperature,  —(A  +  a)°,  for  a  shorter  time,  X  —  x. 
Thus,  Clepsine  complana  resists  —  8°C.  for  15  minutes  ;  —  5°C.  for  90  minutes. 
So  Planorbis  corneus  resists  —  7°  for  5  hours,  but  —  5°  for  48  hours.  Again, 
Musca  domestica  can  resist  —  12°  for  5  minutes ;  —  8°  for  20  minutes ;  and 
—  5°C.  for  40  minutes.  (ROEDEL,  '86.)  Since  many  authors  have  little  re- 
garded the  duration  of  action  of  the  cold,  their  determinations  have  little 
scientific  value. 

t  The  importance  of  this  is  illustrated  by  some  experiments  of  SACHS 
('60,  p.  177),  who  found  that  the  leaves  of  the  beet  or  cabbage  frozen  at  from 
-  4°  to  -  6°  died  if  they  were  thawed  in  air  at  2°  or  3°,  or  in  water  at  6°  to 
10° ;  but  lived  when  slowly  thawed  in  water  at  0°.  In  general,  the  more  gradual 
the  thawing,  the  lower  the  fatal  temperature. 


244 


HEAT  AND   PROTOPLASM 


[Cn.  VIII 


TABLE   XX* 

DETERMINATIONS  OF  THE  ULTRAMINIMUM  OF  ORGANISMS  REARED  UNDER 
NORMAL  CONDITIONS 


SPECIES. 

MINIMUM 
TEMPEBATUEE. 

CONDITIONS 
OP  EXPERIMENT. 

AUTHORITY. 

Plant  cells. 
Trad.esc3.ntia    

—  14°  + 

In    water,    rapidly  i 

—  14°  — 

frozen 
In  air,  rapidly  fro-  f 

KUHNE,  '64,  p.  100 

—   1° 

zen 

Fully  frozen  cautious- 

STRASBURGER    '78 

Swarm-spores    (Proto- 
coccus)       

0=  to  —  1° 

ly  thawed 

p.  612 
COHN,  '50,  p.  720 

Protozoa. 
Amoeba  

0°  — 

Rapidly     frozen     on 

KUHNE  '64  pp  46-47 

Animal  tissues. 
White  blood  corpuscles  : 

of  Amphibia          . 

f  —  2°  to  —  3° 

1 

slide  over  ice  and 
salt 

• 
During  8  hours;  warm- 
ed rapidly 

SCHENK,  '69,  p.  26 

of  rabbit  

-r 

-   3° 

For    a    short    time; 
warmed  rapidly 
During  15  minutes 

"    26  * 

«                      «      Qg 

Saliva  corpuscle  .... 
Red  blood  corpuscle    . 

Spermatozoa  i 
of  Amphibia  

-6°  to  -8° 

-15°  + 

_  40  to  _  70 

Over  60  minutes 

"     27 
POUCHET,  '66,  p.  18 

SCHENK  '69  p  29 

of  Mammalia  .... 
of  frog  

—   6°  — 
_  8°  to  —  10°  — 

Returned  to  activity 
on  thawing 

"    30 

of  frog 

—  10°  to     12° 

of  man  

—  17° 

Gradually  thawed 

p.  353 

Eggs  of  Amphibia  .  .  . 

Ciliated  epithelium  of 
Anodonta   .... 

-  7° 

,     , 

i      —  3° 

During  1  hour 
Subjected  a  very  short 
time 

183 
SCHENK,  '69,  p.  28 
ROTH,  '66,  p.  189 

«              «      ion 

[ 

minutes 

*  Temperatures  all  in  degrees  Centigrade.  —  before  a  number  indicates  below 
zero,  -  or  +  after  a  number  indicates  that  the  true  lethal  temperature  lay 
slightly  below  or  above  that  number.  (A)  indicates  that  the  organism  was  in  air ; 
(W),  in  water. 


§3] 


TEMPERATURE-LIMITS  OF   LIFE 


245 


SPECIES. 

MINIMUM 
TEMPERATURE. 

CONDITIONS 
OF  EXPERIMENT. 

AUTHOKITY. 

Platy  helminths. 
Dendroccelum  lacteum 

^fo^usca. 
Helix  hispida 

0°  to  —  1° 

—   8° 

Suddenly  or  gradually 
subjected,    till    ice 
forms 

During  30  minutes 

ROEDEL,  '86,  p.  207 
"             "      191 

Helix  pomatia  
Helix  pomatia  . 

—  10° 
(—  14°  to—  18°)+ 

During  600  minutes 
Gradually  frozen  for 

"      192 
POUCHET  '66  p  28 

Helix  hortensis  .... 
Helix  aspera        .  .  . 

(—14°  to  —18°)+ 
(—14°  to  —18°)+ 

180    minutes,    and 
then  thawed 
During  180  minutes 
"      180        " 

<«              «« 
«              «« 

Planorbis    

-   7° 

"      300        "  (A) 

ROEDEL,  '86,  p.  212 

Limnaja    

—   7° 

"      180        "  (A?) 

"             "      212 

Pulmonate  embryos    . 
Limax 

(Pto  —  1° 

—  17°+ 

"  Died  upon  freezing  " 
(WandA) 
During  2  hours  (A) 

"      212 
POUCHET  '66  p  26 

Annelida. 
Aulastomum  gulo  .  .  . 

Clepsine  complanata  . 
'  '  Leech  '  ' 

2° 

—   5° 
—  6° 

During  12  to  15  hours 
(W) 
During  90  minutes  (  W) 

* 

ROEDEL,  '86,  p.  206 

"      213 
DOENHOFF  '72  p  725 

Inseeta. 

Apis  mellifica  

—  15° 

utes"  (W) 
During  ^10  minutes 

ROEDEL,  '86  p  212 

Apis  mellifica 

—  1  5° 

DOENHOFF  '72  p  7^4 

Formica  rufa    
Pelopaeus  (chrysalis)  . 

Lema  sp  

-1.5° 

-28J- 

—   6° 

"      180  minutes 
Out-of-doors,       with- 
stood this  tempera- 
ture 
During  30  minutes 

ROEDEL,  '86,  p.  196 
WYMAN,  '56,  p.  157 

ROEDEL,  '86  p.  197 

Psederus  riparius  .  .  . 
Phytonomus  sp  
Alelolontha 

-   4D 
-12° 

—  18°  + 

"      45 
"      90 
"    1°0        "     (A) 

"      197 
ii      197 

POUCHET  '66  p  26 

Melolontha  (larva)   .  . 
Cetonia 
Hydropbilus  j 
Dvtiscus  

-15°  + 
-17°  + 

-   4° 

"    180        "     (A) 
"    120        "     (A) 
"      60        "     (A) 

"      26 
"     26 
KOCHS,  '90,  p.  682 

Vanessa  cardui,  larva 
Vanessa  io,  larva  .  .  . 
Smerintbns  populi    .  . 
Ocneria  dispar 

—  15° 

-173  + 
-10° 
-   4D 

"    600 
"    120 
"    150 
"      30        " 

ROEDEL,  '86,  p.  212 
POUCHET,  '66,  p.  27 
ROEDEL,  '86,  p.  212 
"             "      212 

Culex  pipiens,  larva    . 
Musca    

|  3 

_  50  to  —  10° 

"      60 
"    180        " 

"      212 
DOENHOFF,  '72,  p.  725 

Alusca  dom 

5° 

"         00             " 

ROEDEL   '86  p  201 

Various  insects   .... 

0° 

"    2  to  30  minutes 
(on  ice) 

PLATEAU,  '72,  p.  98 

246 


HEAT   AND   PROTOPLASM 


[CH.  VIII 


SPECIES. 

MINIMUM 
TEMPERATURE. 

CONDITIONS 
OP  EXPERIMENT. 

AUTHORITY. 

Arachnida. 
Phalangium  opilio    .  . 
Tegenaria  domestica  . 
Argyroneta  aquatica  . 
Hydrachna  cruenta  .  . 

-   9° 

—   6° 
.       -   4° 
-    4° 
—  2°  to  —  3° 

During  60  minutes 
"      60 
"    180 
"      30 
"    480        " 

ROEDEL,  '86,  p.  201 
"      201 
"      201 
"              "      201 

DOENHOFF,'72,p.724 

Crustacea. 
Cyclops  quadricornus  . 
Cyclops  spirillum  .  .  . 

Daphnia  pulex    .... 

0° 
-  6° 

0° 

1        "(TF) 

"    120        "(IF) 

f 
OF)  •! 

PLATEAU,  '72,  p.  300 
ROEDEL,  '86,  p.  201 
"      201 

Gammarus  pulex  .  .  . 
Asellus  aquaticus  .  .  . 
Astacus  fluviatilus  .  . 

Vertebrata. 
Rana  esculata  

0° 
0° 
—  11.5° 

—  4°  to  —  10° 

"      30        "(TF) 

(TF)| 
"      a  day       (A) 

"    180  minutes  (A) 

PLATEAU,  '72,  p.  300 
ROEDEL,  '86,  p.  205 
PLATEAU,  '72,  p.  299 
ROEDEL,  '86,  p.  205 
POUCHET,  '66,  p.  32 

«                «      19 

Summarizing  these  conditions,  we  find  that  the  following 
organisms,  even  when  thawed  out  carefully,  are  killed  by  sub- 
jecting to  a  temperature  of  between  0°  and  —  5°  for  60  minutes: 
Amoeba,  swarm-spores,  white  blood  corpuscles  of  Amphibia, 
planarians,  pulmonate  embryos,  small  leeches,  certain  entomos- 
tracans,  and  some  insects  and  spiders.  These  organisms  are  all 
either  soft  bodied  or  of  small  size,  and,  excepting  animals  which, 
like  the  bees,  live  in  protected  situations,  they  do  not  winter 
over  in  our  northern  temperate  countries.  The  following 
species,  on  the  other  hand,  resist  —  10°  for  at  least  60  minutes : 
some  snails  (possibly),  the  beetles  Melolontha  (perhaps)  and 
Phytonomus,  the  Vanessa  larva,  Pelopseus  chrysalis,  and  the 
crayfish,  —  all  protected  by  a  thick  covering,  or  of  rather  large 
size.  The  reason  why  large  size  and  thick  covering  should 
increase  resistance  is  not  far  to  seek,  —  both  conditions  tend 
to  prevent  the  rapid  loss  of  heat,  —  to  defend  the  body  from 
freezing  through  and  through. 

Another  cause  of  variation  in  resistance  to  cold  is,  doubtless, 
the  amount  of  water  in  the  protoplasm.  I  have  already  referred 
to  this  cause  as  explaining  the  fact  that  dry  seeds  and  spores 


§  3]  TEMPERATURE-LIMITS  OF  LIFE  247 

can  withstand  almost  any  temperature.*  MULLER-THURGAU 
("80)  found  that  the  "  succulent  labellum  of  Phajus  freezes  at 
—  0.56°C.  ;  the  succulent  leaf  of  Sempervivum,  at  —0.7°; 
the  potato  tuber,  at  —  1°  ;  the  leaf  of  Tradescantia  mexicana, 
at  —  1.16°  ;  the  ivy  leaf,  at  —  1.5°;  the  leaves  of  Pinus  austri- 
aca,  at  —  3.5°;  young  shoots  of  Thujopsis,  at  —  4°."  (ViXES.) 
In  this  series  of  plant  tissues,  we  see  that  the  more  succulent 
the  tissue,  the  higher  its  ultraminimum.  Possibly  the  reason 
why  spermatozoa  have  so  low  an  ultramaximum,  despite  their 
small  size,  is  on  account  of  the  denseness  of  their  protoplasm. 

Not  all  variations  in  ultraminimum  temperature  are,  however, 
explicable  upon  the  ground  of  difference  in  size,  body-covering, 
or  density  of  plasm.  The  interpretation  of  the  difference  in 
sensitiveness  to  cold  of  the  honey  bee  (Apis  melifica)  and  the 
red  ant  (Formica  rufa),  between  Bombyx  on  the  one  hand  and 
Smerinthus  and  Vanessa  on  the  other,  must  wait  for  further 
knowledge. 

The  question  now  arises,  what  is  the  cause  of  death  in  organ- 
isms and  protoplasm  which  succumb  to  low  temperatures  ? 
With  the  higher  animals  the  immediate  cause  is  doubtless  in 
part  asphyxia  resulting  from  a  stoppage  in  the  flowing  of  the 
frozen  blood  plasma,  and  in  part  the  destruction  of  the  red 
blood  corpuscles,  as  well  as  the  white. f  With  the  simpler 
organisms,  like  planarians,  Protozoa,  or  Tradescantia  hair-cells 
the  case  is  different.  An  insight  into  the  changes  which  pro- 
duce death  in  such  organisms  may  be  gained  from  KUHXE'S 
('64,  p.  101)  description  of  the  effect  of  a  temperature  of  —  14° 
on  Tradescantia  hair-cells.  The  frozen  hairs  were  placed  in 
water  and  observed  under  the  microscope.  "  The  appearance," 

*  Striking  cases  are  on  record  of  the  resistance  of  gemmules,  or  "animal 
spores,"  to  cold.  Thus,  WELTNER  ('93,  p.  276)  saw  gemmules  of  Spongilla 
fragilis  frozen  in  an  aquarium  from  December  26  to  January  24,  from  the  end 
of  January  to  February  5,  from  February  20  to  March  6,  and  from  March  12 
to  24  ;  the  intervals  being  occupied  by  thawings.  Yet  these  gemmules  produced 
young  sponges.  In  other  cases,  a  certain  amount  of  freezing  favors  the  subse- 
quent development  of  gemmules,  e.g.  those  of  fresh-water  Bryozoa  (BRAEM,  '90, 
p.  83)  and  the  eggs  of  the  silk-worm  (DUCLAUX,  '71). 

t  POUCHET  ('66,  p.  18)  found  that  when  blood  of  the  frog  was  let  fall  into  a 
capsule  at  a  temperature  of  -  15°  few  of  the  red  corpuscles  were  uninjured.  In 
most  the  nuclei  had  been  cast  out  into  the  plasma. 


248  HEAT  AND  PROTOPLASM  [Cn.VIII 

says  KUHKE,  "  was  very  remarkable,  for  there  was  no  trace  of 
the  protoplasmic  network;  but  the  violet  cavity  of  the  cell  con- 
tained, in  addition  to  the  naked  nucleus,  a  large  number  of 
separate  round  drops  and  lumps."  In  this  case,  the  separate 
pieces  eventually  became  active  again,  so  that  the  protoplasm, 
though  nearly  killed,  was  not  quite  so. 

The  phenomena  seen  by  KUHKE  so  closely  resemble  those 
produced  in  the  same  kind  of  cells  by  the  galvanic  current  and 
other  strong  irritants  as  to  indicate  that  cold  acts  as  an  intense 
irritant.  We  cannot,  however,  conclude  that  cold  acts  in  no 
other  way.  It  is  clear  that  the  expansion  of  forming  ice  in  the 
vacuoles  of  the  protoplasm  must  seriously  disturb  the  structure, 
and,  since  the  whole  matter  has  received  little  attention,  it  is 
possible  that  a  molecular  change  of  some  sort  takes  place  when 
there  is  much  water  in  the  freezing  protoplasm.  To  summarize : 
Death  by  freezing  results  in  the  higher  animals  largely  from 
asphyxia,  and  in  the  simpler  organisms  from  excessive  irritation, 
mechanical  rupture,  and,  perhaps,  other  causes. 

I  shall  now  sum  up  this  section  on  the  effect  of  extremes  of 
heat  and  cold.  As  the  temperature  is  elevated  above  the  opti- 
mum, molecular  changes  occur  in  the  protoplasm  leading  to  its 
contraction.  The  contraction  becomes  more  violent  as  the  tem- 
perature is  still  raised,  until,  finally,  a  new  series  of  molecular 
changes  occur  by  which  the  protoplasm  begins  to  coagulate. 
At  this  point  the  protoplasm  begins  to  lose  its  irritability.  If 
this  process  has  not  proceeded  far,  the  vital  activities  may, 
under  favorable  conditions,  return  (temporary  heat-rigor). 
Beyond  a  certain  point  (death  point)  recovery  is  impossible. 
The  death  point  varies  with  the  species,  but  lies  not  far  from 
the  maximum  natural  temperature  attained  by  the  medium  in 
which  they  live.  On  the  other  hand,  as  the  temperature  is 
diminished  from  the  optimum,  the  chemical  processes  of 
metabolism  decrease  in  vigor  and  come  to  a  standstill  at  about 
the  freezing  point  of  water.  Violent  contractions  accompany 
the  cooling  process,  concomitantly  with  which  the  protoplasm 
breaks  down.  From  this  condition  of  temporary  cold-rigor 
recovery  is  still  possible ;  but  a  little  below,  at  a  point  dependent 
upon  the  size  of  the  body  and  the  diathermous  qualities  of  its 


§-4]     ACCLIMATIZATION  TO  EXTREME  TEMPERATURES     249 

covering,  the  water  of  the  body  begins  to  freeze,  and  in  that 
process,  or  the  subsequent  thawings,  the  protoplasm  undergoes 
a  (partly  mechanical)  change  resulting  in  death.  If  the  body, 
however,  contains  no  water,  freezing  cannot  kill  it. 

Thus  the  effect  of  high  temperatures  is  principally  chemical, 
involving  the  living  plasma ;  that  of  low  temperatures  is  prin- 
cipally mechanical,  involving  the  water  of  the  body.  Both 
raising  and  lowering  the  temperature  act  also  as  irritants.* 
Finally,  the  positions  ,  of  the  maximum  and  minimum  stand  in 
most  intimate  relation  to  the  inorganic  environment  of  the 
organism  and  have  been  molded  to  that  environment. 


§  4.   ACCLIMATIZATION  OF  ORGANISMS  TO  EXTREME 
TEMPERATURES 

The  phenomena  to  be  discussed  in  this  section  fall  naturally 
into  two  subsections:  (1)  acclimatization  to  heat  and  (2)  accli- 
matization to  cold.  They  will  be  considered  in  that  order. 

1.  Acclimatization  to  Heat.  —  Our  study  of  the  maximum 
temperature  which  organisms  reared  under  ordinary  circum- 
stances can  withstand,  led  us  to  the  conclusion  that  few  active 
organisms  can  resist  a  temperature  of  over  45°,  and  for  whole 
groups  like  Coelenterata,  marine  Mollusca,  and  Crustacea,  and 
the  fishes,  40°  is  a  point  of  death.  Yet,  on  the  other  hand,  it 
has  long  been  known  that  there  are  organisms  living  in  certain 
hot  springs  in  waters  of  considerably  higher  temperature.  I 
shall  now  give  in  tabular  form  some  cases  which  I  have 
collected  of  organisms  living  at  or  above  the  normally  lethal 
temperature  of  the  species,  f 

*  Whether  sudden  change  of  temperature  has  an  especial  effect  upon  the 
movement  of  protoplasm  is  a  disputed  question,  which  has  been  answered  posi- 
tively by  DUTROCHET  ('37,  p.  777)  and  HOFMEISTER  ('67,  p.  53)  for  Nitella,  and 
DE  VRIES  ('70,  p.  394)  for  root  hairs  of  Hydrocharis,  but  has  since,  as  a  result 
of  careful  experiments,  been  denied  by  VELTXER  ('76,  p.  214)  for  Nitella  and 
other  plant  cells. 

I  It  is  desirable  that  accurate  data  concerning  the  temperature  of  organisms 
in  hot  springs  should  be  made,  and  we  have,  in  this  country,  unusually  favorable 
conditions  offered  for  this  study,  especially  in  Arkansas,  California,  and  the 
Yellowstone  National  Park.  It  is  to  be  hoped  that  persons  who  have  had  the 
proper  training  should,  when  contemplating  a  visit  to  hot  springs,  provide  them- 


250 


HEAT  AND   PROTOPLASM 


[Cn.  VIII 


TABLE  XXI 
LIST  OF  SPECIES  FOUND  IN  HOT  SPRINGS,  WITH  THE  CONDITIONS  UNDER 

WHICH    THEY    OCCUR 


No.* 

SPECIES. 

TEMP.  C. 

LOCALITY  AND  CONDITION  OF 
LIFE. 

AUTHORITY. 

1 

Chroococcus 

51°  to  57° 

Benton's  Hot  Springs,  Cal. 

WOOD,  '74,  p.  34 

2 

Nostocs  or  Pro- 

93° 

Geysers,  Lake  Co.,  Cal.  ;  not 

BREWER,  '66,  p.  391, 

tococcus 

abundant    at    this    tem- 

also WYMAN,  '67, 

perature 

p.  155 

3 

Nostocs 

51°  to  57° 

Benton's  Hot  Springs,  Cal. 

WOOD,  '74,  p.  34 

4 

Anabsena     ther- 

57° 

Dax,  warm  springs 

SERRES,'80,pp.l3-23 

malis 

5 

Leptothrix 

44°  to  54° 

Carlsbad  Springs 

COHN,  '62,  p.  539 

6 

Oscillaria     or 

54°  to  68° 

Yellowstone     Nat.     Park, 

WEED,  '89,  p.  399 

"Confervse" 

U.S.A. 

7 

" 

54.4° 

Springs,  Bernandino  Sierra, 

BLAKE,  '53,  p.  83 

Cal. 

8 

ii 

57° 

Algeria,  Constantine  prov- 

GERVAIS, '49,  p.  12 

ince,  waters  of  Hammam- 

Meskhoutin 

9 

«< 

57° 

Hot  Springs,  Taupo,  New 

SPENCER,  '83,  p.  303 

Zealand 

10 

« 

60°  to  65° 

Geysers,    Lake    Co.,    Cal., 

BREWER,  '66,  p.  392 

U.S.A. 

11 

" 

60°  to  65° 

Hot  Springs,  Ark.,  U.S.A. 

JAMES,  '23,  II,  p.  291 

(Long) 

12 

" 

71° 

Hot  Springs  at  Banos  Luzon, 

DANA,  '38-'42,  p.  543 

Philippines 

13 

" 

75.5° 

Soorujkoona  Hot  Springs 

HOOKER,  J.  D.  '55,  1, 

p.  24 

14 

« 

81°  to  85° 

Ischia 

EHRENBERG,  '59,  p. 

493. 

15 

i< 

98° 

Iceland 

FLOURENS,    '46,    p. 

934 

16 

" 

? 

Outlet    of    Lake    Furnas, 

DYER,  '74,  p.  324 

Azores. 

selves  with  a  hand  lens,  bottles  of  alcohol  for  preserving  organisms  for  further 
study,  and  an  accurately  calibrated  thermometer.  A  source  of  error  to  be 
guarded  against  lies  in  the  precise  determination  of  the  temperature  of  the  water 
immediately  surrounding  the  organism  observed;  for  in  some  warm  springs  or 
their  outlets  the  surface  water  is  said  to  be  much  warmer  than  the  deeper  layers 
in  which  the  organisms  are  found.  Finally,  if  possible,  it  would  be  desirable  to 
determine  on  the  spot,  experimentally,  the  maximum  temperature  which  these 
organisms  can  withstand.  For  this  determination  some  of  the  methods  referred 
to  on  p.  220  should  be  used. 

'  *  Notes  on  each  of  these  cases  will  be  found  at  the  end  of  this  chapter,  pp. 
263-267. 


§4]     ACCLIMATIZATION  TO  EXTREME  TEMPERATURES     251 


No. 

SPECIES. 

TEMP.  C. 

LOCALITY  AND  CONDITION  OF 
LIFE. 

AUTHORITY. 

Diatoms 

Frequently  associated  with 

other  algae  in  hot  springs 

17 

Physa  acuta 

33°  to  35° 

Sources  of  Dax,  St.  Pierre, 

DUBALEN,  '73,  p.  iv 

France 

18 

Paludina  sp. 

50° 

Thermal    waters,    Abano, 

DE  BLAINVILLE,  '24, 

Padua 

p.  141 

19 

"Bivalve   testa- 

? 

Hot  Springs,  Ark. 

MITCHILL,  '06,  p.  306 

ceous  animal" 

20 

Rotifera  and  An- 

44°  to  54° 

Carlsbad  Springs,  Bohemia 

COHN,  '62,  p.  539 

guillulidse 

21 

Anguillulidae 

45° 

Aix,  springs 

DE  SAUSSURE,  1796, 

V,  p.  13,  §  1168 

22 

" 

81° 

Ischia,  in  hot  springs 

EHRENBERG,  '59,  p. 

494 

23 

Cypris  balnearia 

45°  to  50.5° 

Hammam-Meskhoutin 

MONIEZ,  '93,  p.  140 

24      Stratiomys  larva 

69° 

In    hot   spring,    Gunnison 

GRIFFITH,  '82,  p.  599 

B 

Co.,  Col. 

2.-. 

" 

? 

In  hot  spring,  Uinta  Co., 

BRUNER,  '95 

Wyo. 

26 

"  Water  beetle  " 

44.4° 

In    warm    spring,    India; 

HOOKER,  J.  D.  '55,  p. 

abundant 

24 

27 

« 

? 

Hot    spring,   Port    Holier, 

DALL,  W.  H.   (per- 

Alaska 

sonal  letter) 

28 

Barbels 

34° 

? 

BERT,  '77,  p.  169 

29 

Frogs 

38° 

"  Baths  of  the  Pise  " 

SPALLANZANI,  1787, 

Tom.  I,  p.  55 

To  summarize  :  Protista  are  stated  to  have  been  found  in 
nature  in  water  at  temperatures  far  above  60°  C.  The  most 
striking  cases  are  of  Oscillaria  and  "  Conferva  "  from  several 
localities,  which  resist  nearly  up  to  the  boiling  point  of  water. 
The  closely  allied  Nostocs  are,  perhaps,  next  most  abundant 
and  resistant,  reaching  93°  (possibly  Protococcus)  in  the  Cali- 
fornia geysers.  Metazoa  are  stated  to  live  at  temperatures 
far  above  45°.  Although  some  doubt  has  been  cast  on  No.  22 
by  HOPPE-SEYLEK'S  inability  to  confirm  EHRENBERG'S  observa- 
tions, the  case  seems  established  of  Cypris  thriving  at  45°  to 
50.5°.  Very  extraordinary  are  the  observations  Nos.  24  and 
25  on  Stratiomys  Iarva3,  which,  however,  are  sadly  in  need  of 
confirmation  by  competent  observers.  Leaving  out  of  account, 
for  the  moment,  the  less  well  established  cases,  there  still 
remains  abundant  evidence  that  organisms  can  live  and  thrive 


252  HEAT   AND   PROTOPLASM  [Ck.  VIII 

in  hot  springs  at  a  temperature  near  or  above  that  which  proves 
fatal  to  their  close  allies. 

No  one  doubts  that  in  all  the  cases  cited  above  the  individuals 
living  in  hot  springs  have  been  derived  from  ancestors  which 
lived  in  water  whose  temperature  rarely  exceeded  40°  C.  The 
race  has  therefore  become  acclimatized,  and  the  question  arises  : 
How  has  that  acclimatization  been  effected  ? 

Now  experiments  have  shown  that  organisms,  when  gradually 
accustomed  thereto,  may  resist  a  temperature  which  would  have 
killed  them  if  they  had  been  suddenly  subjected  to  it.  There- 
fore it  seems  probable  that  the  acclimatization  of  organisms  to 
hot  springs  has  been  a  slow,  long-continued  process,  during 
which  they  have  become  gradually  accustomed  to  higher  and 
higher  temperatures,  probably  attaining  the  hot  springs  by 
slowly  advancing  up  their  effluent  streams. 

This  adaptation  may  have  taken  place  without  selection, 
purely  by  the  capacity  of  individual  adaptation  which  organ- 
isms possess.  That  individual  adaptation  is  sufficient  to  account 
for  the  vitality  of  organisms  in  hot  springs  has  been  shown  by 
experiment.  DUTROCHET  ('37,  p.  777)  observed,  long  ago, 
that  an  organism  which  at  first  seemed  injured  by  a  high 
temperature  gradually  regained  activity  while  still  subjected 
thereto. 

Thus,  he  found  that  the  current  of  Nitella  was  at  first  diminished  by 
raising  it  to  27°  C.,  but  it  soon  became  rapid  again ;  raised,  now,  to  34°,  the 
circulation  began  to  fall  off  again,  but  in  a  quarter  of  an  hour,  the  same 
temperature  continuing,  the  circulation  became  very  rapid.  This  phenome- 
non was  repeated,  also,  at  40°.  Similarly,  HOFMEISTER  ('67,  p.  53)  brought 
Xitella  flexilis  suddenly  from  -f-  18.5°  to  4-  5°C.  The  streaming  movements 
ceased.  After  staying  15  minutes  in  the  cooler  room,  however,  the  rotation 
of  protoplasm  recovered. 

Much  more  important,  however,  are  the  remarkable  experi- 
ments of  DALLINGER  ('80).  He  kept  Flagellata  in  a  warm 
oven  for  many  months.  Beginning  with  a  temperature  of 
15.6°  C.,  he  employed  the  first  four  months  in  raising  the  tem- 
perature 5.5° ;  this,  however,  was  not  necessary,  since  the  rise 
to  21°  can  be  made  rapidly,  but  for  success  in  higher  tempera- 
tures it  is  best  to  proceed  slowly  from  the  beginning.  When 
the  temperature  had  been  raised  to  23°,  the  organisms  began 


§  4]     ACCLIMATIZATION  TO  EXTREME  TEMPERATURES      253 

dying,  but  soon  ceased,  and  after  two  months,  the  temperature 
was  raised  half  a  degree  more,  and  eventually  to  25.5°.  Here 
the  organisms  began  to  succumb  again,  and  it  was  necessary 
repeatedly  to  lower  the  temperature  slightly,  and  then  to 
advance  it  to  25.5°,  until,  after  several  weeks,  unfavorable 
appearances  ceased.  For  eight  months,  the  temperature  could 
not  be  raised  from  this  stationary  point  a  quarter  of  a  degree 
without  unfavorable  appearances.  During  several  years,  pro- 
ceeding by  slow  stages,  DALLINGER  succeeded  in  rearing  the 
organisms  up  to  a  temperature  of  70°  C.,  at  which  the  experi- 
ment was  ended  by  an  accident. 

In  this  case  it  is  plain  that  the  high  temperature  acted  upon 
the  same  protoplasm  at  the  end  of  the  experiment  as  it  did 
at  the  beginning.  But  while  the  protoplasm  at  the  beginning 
of  the  experiment  was  killed  at  23°  C.,  at  the  end  it  withstood 
70°.  It  will  be  seen  that,  by  gradual  elevation  of  the  tempera- 
ture, Flagellata  may  become  acclimated  to  a  temperature  of 
water  far  above  that  which  they  can  withstand  when  taken 
directly  from  out  of  doors,  and  approaching  that  of  the  hottest 
springs  containing  life. 

A  series  of  experiments,  less  extensive  than  that  of  DAL- 
LIXGER,  was  carried  on  by  Dr.  CASTLE  and  myself  ('95,  pp. 
236-240)  upon  the  tadpoles  of  our  common  toad,  Bufo  lentigi- 
nosus.  Recently  laid  eggs  were  divided  into  two  lots :  one 
lot  was  kept  in  a  warm  oven  at  a  constant  temperature  of  24° 
to  25°,  others  at  about  15°  C.  Both  lots  developed  normally, 
but  the  former  much  the  more  rapidly.  At  the  end  of  4 
weeks  the  point  of  heat-rigor  was  ascertained  for  each  lot,  by 
gradually  heating  (in  from  5  to  10  minutes)  the  water  contain- 
ing them,  until  the  tadpoles  showed  no  response  to  stimulus, 
but.  upon  cooling,  regained  activity.  The  result  was  that  the 
toad  tadpoles  had  gained  an  increased  capacity  to  heat.  For 
when  they  were  reared  at  a  temperature  of  about  15°  C.,  every 
tadpole  went  into  heat-rigor  at  41°  C.,  or  below;  whereas, 
when  they  were  reared  at  24°  to  25°,  a  temperature  10° 
higher,  no  tadpole  died  under  43°,  the  average  increase  of 
resistance  being  3.2°.  This  increased  capacity  of  resistance 
was  not  produced  by  the  dying  off  of  the  less  resistant  indi- 
viduals, for  no  deaths  occurred  in  these  experiments  during 


254  HEAT  AND  PROTOPLASM  [Cn.  VIII 

the  gradual  elevation  of  the  temperatures  in  the  cultures.  The 
increased  resistance  was  due,  therefore,  to  a  change  in  the 
protoplasm  of  the  individuals. 

The  question  now  arose  :  In  how  far  is  this  change  in  the 
protoplasm  permanent?  Will  a  return  of  the,  individuals  to 
cool  water  cause  a  return  to  the  old  point  of  heat-rigor?  We 
made  a  few  experiments  on  this  subject  which  showed  that 
tadpoles  which  during  33  days  in  warm  water  have  acquired 
an  increased  resistance  of  3.2°  lose  part  of  that  acquired  resist- 
ance during  17  days'  sojourn  in  cooler  water.  But  the  loss 
is  a  very  slow  one.  The  effect  of  the  high  temperature  on  the 
tadpoles  is  not,  therefore,  transitory,  but  persists  —  we  have 
not  been  able  to  determine  how  long  —  after  the  cause  has  been 
removed. 

So  we  may  conclude  :  Individual  organisms  have  the  capacity 
of  becoming  adapted  to  a  high  degree  of  temperature,  so  that  a 
temperature  which  normally  is  fatal  may  be  withstood.  This 
adaptation  of  the  individual  accompanies  the  subjection  of 
organisms  to  temperatures  higher  than  those  to  which  they 
have  already  become  accustomed.  This  capacity  exists  among 
both  Protozoa  and  Metazoa.  The  effect  of  the  elevated  tem- 
perature persists  (though  in  diminished  degree)  a  considerable 
time  after  the  individual  has  been  restored  to  a  lower  tempera- 
ture. 

Acclimatization  may  show  itself  not  only  in  the  change  of 
the  maximum  temperature,  but  also  in  the  elevation  of  the 
optimum.  This  is  shown  by  the  following  experiments  of 
MENDELSSOHN  ('95,  p.  19).  When  Paramecia  are  placed  in  a 
trough  whose  temperature  is  24°  to  28°  at  one  end  and  36°  to 
38°  at  the  other,  they  are  found  to  collect  at  the  cooler  end, 
which  indicates  that  the  temperature  of  that  end  lies  nearer 
their  optimum.  If,  however,  the  Paramecia,  while  uniformly 
distributed  in  the  trough,  are  subjected  to  a  uniform  tempera- 
ture of  36°  to  38°  for  from  4  to  6  hours,  and  then,  in  the  same 
trough,  to  a  temperature  varying  from  24°  at  one  end  to  36°  at 
the  other,  they  no  longer  collect  at  the  usual  optimum  of  24°  to 
28°,  but  at  30°  to  36°.  Thus  in  4  to  6  hours,  by  the  action  of 
a  temperature  of  36°  to  38°,  the  optimum  has  been  raised  6° 
to  8°. 


§4]     ACCLIMATIZATION  TO  EXTREME  TEMPERATURES     255 

Since  experiments  have  proved  the  fact  of  acclimatization,  it 
now  remains  to  determine,  if  possible,  its  cause ;  to  answer  the 
question,  by  virtue  of  what  property  can  organisms  which,  like 
Flagellata,  normally  perish  at  45°  C.  come  to  live  at  70°  or 
even  higher  temperatures  ?  We  have  seen  that  death  at  high 
temperatures  is  apparently  due  to  coagulation  of  certain  proteids 
in  the  protoplasm  which  undergo  a  chemical  change  at  between 
45°  and  50°  C.  Now,  although  the  matter  has  not  yet  been 
studied  in  these  proteids,  it  has  been  shown  for  egg  albumen 
that  in  proportion  as  it  is  dried  its  coagulation  point  rises,  as 
the  following  table  from  LEWITH  ('90)  shows  :  — 


EGG  ALBUMEN. 


COAGULATION  TEMPERATURE. 


In  aqueous  solution 
With  25%  water 
With  18%  water 
With  6  %  water 
Without  water 


56°  C. 

74°  to  80°  C. 

80°  to  90°  C. 

145°  C. 

160°  to  170°  C. 


Since  the  coagulation  point  of  egg  albumen  is  raised  by  dry- 
ness,  it  is  very  probable  that  a  similar  cause  may  act  to  raise 
the  coagulation  point  of  protoplasm  in  organisms  of  hot  springs. 
Experimental  studies  are  much  needed  upon  this  point.  Mean- 
while it  can  be  said  that  one  of  the  qualities  which  gives  ca- 
pacity of  resistance  to  high  temperatures  is  dryness.  I  shall  now 
cite  some  cases  that  I  have  collected,  which  prove  this  point. 
It  has  been  found  that  while  moist  yeast  is  killed  at  a  tempera- 
ture below  60°,  dry  yeast  may  be  heated  to  100°  C.  without 
losing  its  vitality  (SCHUTZENBERGER,  '79,  p.  162).  Damp 
uredo-spores  are  killed  at  58.5°  to  60°  C.,  but  dry  ones  with- 
stand up  to  128°  (HOFFMAN,  '63);  and  dry  spores  of  some 
molds  up  to  120°  (PASTEUR,  '61,  p.  81).  According  to  DAL- 
LIXGER  ('80,  pp.  11-14),  the  dry  spores  of  various  Flagellata 
are  capable  of  withstanding  a  temperature  from  10°  to  27°  C. 
higher  than  that  which  these  spores  can  resist  in  fluid.  Accord- 
ing to  DOYERE  ('42,  p.  29),  various  animalcules  (Rotifers, 
Tarcligrades)  which  cannot  in  water  withstand  a  temperature 
of  50°  C.  may,  after  long  drying,  be  heated  in  air  to  120°  C. 


256  HEAT   AND  PROTOPLASM  [Cn.  VIII 

(rarely  to  125°)  without  all  dying.  The  foregoing  cases  show 
clearly  that  increased  resistance  capacity  is  frequently  gained 
by  subjecting  the  protoplasm  of  the  organism  to  dryness. 

But  there  are  other  conditions  under  which  the  living  sub- 
stance shows  extraordinary  resistance  capacity.  In  general,  as 
is  well  known,  the  spores  of  organisms  withstand  higher  tem- 
peratures than  the  motile  stage,  when  both  are  in  water.  This 
rule  holds  for  many  cases  :  The  spores  of  some  bacteria  may  be 
heated  for  a  time  above  100°  C.  without  killing  them,  although 
their  motile  stage  is  killed  by  50°  to  52°  (LEWITH,  '90). 
DALLINGER  and  DRYSDALE  ('74,  p.  101)  and  DALLINGER 
('80,  pp.  13,  14)  have  determined  maximum  temperatures  for 
several  Flagellata  and  their  spores  in  water.  While  none  in 
the  motile  stage  could  withstand  a  temperature  higher  than  61°, 
the  spores  in  water  withstood  maximum  temperatures  varying 
between  65.5°  and  131°  for  the  different  species. 

Have  the  high  resistance  capacity  of  dry  protoplasm  and  that 
of  spores  a  common  cause  ?  Or,  in  other  words,  is  the  proto- 
plasm of  spores  especially  free  from  water  ?  Many  observations 
make  it  appear  probable  that  this  is  so. 

Thus  in  the  case  of  bacteria,  the  protoplasm  of  the  spore 
stage  is  optically  denser  and  occupies  less  space  than  in  the 
motile  stage.  (Cf.  LEWITH,  '90.) 

In  the  case  of  the  ciliate  Infusoria,  the  larger  size  of  the 
protoplasmic  mass  makes  the  comparison  of  the  condition  of 
the  protoplasm  in  the  two  stages  easier.  We  glean  the  facts 
from  BUTSCHLI  ('89,  pp.  1652-1654).  As  the  process  of  encyst- 
ment  proceeds,  the  contractile  vacuole  continues  to  function, 
the  intervals  between  its  contractions  gradually  increase,  and 
finally  it  disappears  some  time  after  the  encystment  is  com- 
pleted. Hand  in  hand  with  these  changes  goes  a  gradual  con- 
densation of  the  protoplasm.  This  condensation  BUTSCHLI 
believes  to  be  due  to  an  excretion  of  water  from  the  proto- 
plasm. 

In  Actinosphserium  the  change  from  the  richly  vacuolated 
motile  form  to  the  encysted  condition  is  even  more  marked. 
As  BRAUER  ('94,  p.  193)  has  shown,  the  protoplasmic  mass 
becomes,  during  the  process  of  encystment,  smaller  and  denser. 
The  loss  of  water  from  the  protoplasm  is  without  doubt  due  to 


§4]     ACCLIMATIZATION  TO  EXTREME  TEMPERATURES     257 

the  continued  activity  of  the  contractile  vacuole  at  a  time  when 
110  fluids  are  being  taken  into  the  protoplasmic  body. 

From  the  foregoing  considerations  it  appears  probable  that 
one  of  the  important  characters  of  "  spores  "  is  the  diminished 
amount  of  free  water  held  in  the  protoplasm;  or,  in  other 
words,  its  dryness.  This  dryness  of  the  coagulable  substance 
would  seem  to  be  cause  of  its  higher  resistance. 

So  far  the  evidence  seems  complete.  Whether,  however,  loss 
of  water  is  the  ultimate  cause  of  the  high  resistance  capacity 
of  hot-spring  organisms  or  of  those  gradually  acclimatized  is 
still  uncertain.  Analogy  renders  it  highly  probable  that  such 
is  the  case. 

2.  Acclimatization  to  Cold.  —  Just  as  organisms  may  become 
acclimatized  to  high  temperatures,  so  also  may  they  live  in  very 
cold  regions.  I  cite  a  few  examples  :  Several  species  of  Pro- 
tista are  said  to  live  in  the  Alps  above  the  snow  line,  coloring 
the  snow  red.  (SHTJTTLEWORTH,  '40.)  A  tardigrade  is  found 
in  the  same  locality.  Certain  insects  live  on  or  in  the  snow  or 
ice.  Thus  Desoria  glacialis  (or  glacier  flea)  lives  on  the  Swiss 
glaciers,  and  on  the  snow  live  Podura  hiemalis,  Trichocera 
brumalis  (when  the  temperature  is  "below  the  freezing  point," 
FITCH,  '46,  p.  10),  and  other  species  of  Trichocera  and  Podura. 
Cf.  also  Boreus  hiemalis  and  B.  brumalis  (FiTCH).  Although 
swarm-spores  are  usually  extremely  sensitive  to  cold,  STRAS- 
BUEGER  ('78,  p.  613)  cites  a  case  of  a  marine  alga  in  which 
they  were  being  formed  and  thrown  out  when  the  temperature 
of  the  water  was  between  —1.5°  and  —1.8°  C. 

Increased  resistance  to  cold  seems  often  the  result  of  the 
action  of  cold  on  the  organism.  Thus,  while  SCHWARZ  ('84, 
p.  69)  found  that  Euglense  gathered  in  the  summer  time  were 
not  responsive  below  +  5°  to  -f-  6°  C.,  ADERHOLD  ('88,  p.  320) 
found  that  Euglense  gathered  in  the  winter  would  respond 
even  at  0°.  We  may  say,  the  winter  cold  had  in  some  way 
lowered  the  heat  attunement  of  these  Protista. 

In  seeking  for  an  explanation  of  acclimatization  to  cold  we 
should  recall  that  the  cause  of  death  from  cold  is  chiefly  the  freez- 
ing of  water  in  the  protoplasm,  and  the  irritation  of  excessive 
cold.  Accustomed  to  great  cold,  protoplasm  would  doubtless 
be  no  longer  irritated  by  it ;  whether  under  these  circumstances 


258  HEAT   AND  PROTOPLASM  [Cn.  VIII 

it  would  contain  less  water  is  a  question  which  lacks  an  experi- 
mental answer. 

The  conclusion  from  the  results  offered  in  this  section  is 
this :  protoplasm  may  become  so  modified  through  the  action 
of  excessive  heat  or  cold  that  it  is  no  longer  killed  at  the  ordi- 
nary fatal  temperatures.  This  result  is  partly  due  to  the  fact 
that  it  is  then  not  so  strongly  irritated  by  these  extreme  tem- 
peratures, and  partly  owing  to  the  fact  that  the  coagulation 
and  freezing  points  have  been  shifted,  possibly  through  loss 
of  water. 

§  5.    DETERMINATION  OF  THE  DIRECTION  OF  LOCOMOTION 
BY  HEAT  —  THERMOTAXIS 

Our  knowledge  of  this  subject  is  still  in  its  infancy  and  de- 
pends chiefly  upon  the  observations  of  STAHL  ('84),  VER- 
WORN  ('89,  pp.  67-68),  GRABER  ('83  and  '87),  LOEB  ('90,  p.  43), 
DE  WILDEMANN  ('94),  and  MENDELSSOHN  ('95).  The  first 
two  and  the  last  two  mentioned  have  employed  Protista,  and 
we  may  consider  their  work  first. 

STAHL'S  studies  were  made  upon  Myxomycetes.  He  used 
two  beakers,  of  which  one  was  filled  with  water  at  7°;  the 
other  with  water  at  30°.  These  were  placed  near  each  other, 
and  a  strip  of  filter-paper,  on  which  lay  the  plasmodium  of 
JEthalium  septicum,  was  stretched  between  them.  The  two 
ends  of  the  strip  with  the  corresponding  ends  of  the  plasrno- 
dium  hung  into  the  two  glasses.  The  result  was  that  the 
plasmodium  moved  from  the  colder  water  toward  the  warmer, 
although  before  the  experiment  it  was  moving  in  the  opposite 
direction.  WORTMANN  ('85)  added  the  observation  that  when 
the  warmer  temperature  rose  above  36°  a  repellent  action  of 
the  warmer  water  was  discernible. 

VERWORN  experimented  chiefly  with  Amoeba.  The  difficulty 
in  this  operation  depended  upon  the  necessity  of  warming  only 
a  part  of  the  body  of  so  small  an  animal.  He  used  a  glass  plate 
of  5  sq.  cm.  area,  to  the  upper  surface  of  which  was  glued  a 
piece  of  black  paper,  in  which  had  been  cut  a  rectangular  open- 
ing, 3  sq.  mm.  large,  and  with  very  sharp  edges.  This  plate 
was  placed  on  the  stage  of  the  microscope  so  that  the  hole  lay 


§  5]  THERMOTAXIS  259 

in  the  rays  of  the  infalling,  concentrated  light  of  midsummer, 
reflected  from  the  mirror.  Upon  the  black  paper  was  placed 
the  cover-glass  with  the  amoeba  in  a  drop  of  water.  The  light 
from  the  mirror  was  cut  off  until  the  amoeba,  in  its  migrations, 
lay  half-way  over  the  edge  of  the  orifice.  Then  concentrated 
light  was  let  through  the  slit.  A  small  part  of  the  body  was 
still  moved  across  the  line  of  demarcation;  then  for  a  moment 
movement  ceased  and  a  few  seconds  after  the  protoplasm  of  the 
amoeba  began  to  flow  backwards.  In  from  10  to  30  seconds 
the  amoeba  was  wholly  in  the  dark  again.  Similarly,  when  the 
cover-glass  was  moved  so  that  the  amoeba  was  brought  half-way 
over  the  open  orifice  it  retreated  into  the  dark.  Direct  measure- 
ment showed  that  the  temperature  at  the  illuminated  part  was 
40°  to  50°  C.,  whilst  over  the  black  paper  it  was  15°  to  20°  less. 
That  the  movement  was  not  due  to  the  light  was  shown  first 
by  cutting  out,  by  means  of  ice,  the  heat  rays  only.  No  reac- 
tion occurred.  Secondly,  by  cutting  out  the  light  but  not  the 
heat,  by  passing  the  light  through  a  solution  of  iodine  in  CS2 
so  that  only  the  ultra-red  rays  (which  act  like  darkness  to  all 
organisms)  went  through;  the  typical  reaction  occurred  when 
the  temperature  over  the  slit  was  35°.  From  all  of  these  ex- 
periments the  conclusion  seems  justified  —  Amoeba  is  positively 
thermotactic  towards  that  temperature. 

Similar  results  were  obtained  by  VERWORN  with  the  shelled 
Rhizopod  Echinopyxis  aculeata,  and  later  (see  JENSEN,  '93, 
p.  440)  with  Paramecium.  More  complete  studies  on  the 
latter  were,  however,  made  by  MENDELSSOHN,  who  worked  in 
VERWORN'S  laboratory.  MENDELSSOHN  devised  an  excellent 
method  of  study.  A  brass  plate  20  cm.  x  6  cm.  and  4  mm. 
thick  is  properly  supported  in  a  horizontal  position,  and  to  its 
under  face  are  affixed,  transversely,  tubes  through  which  hot 
or  cold  water  may  be  run  from  a  reservoir  placed  at  a  high 
level.  In  the  middle  of  the  plate  a  space  10  cm.  x  2  cm.  and 
2  mm.  deep  is  cut  out  and  into  it  is  fitted  a  glass  or  ebonite 
trough.  Special  thermometers  whose  bulbs  are  coiled  in  the 
plane  of  the  trough,  and  hence  perpendicularly  to  the  stem, 
serve  to  measure  the  temperature  of  the  water  in  the  trough  at 
any  point.  By  means  of  water  running  through  the  transverse 
tubes  either  end  of  the  trough  may  be  heated  or  cooled  as 


260 


HEAT   AND  PROTOPLASM 


[Cn.  VIII 


desired.  Starting  now  with  the  trough  filled  with  infusion 
water,  the  Paramecia  are  seen  to  be  uniformly  distributed 
(Fig.  71,  a).  Hot  water  is  run  through  tubes  under  the  right 
end  of  the  trough.  After  10  minutes  the  thermometers  show 
the  temperature  of  the  water  at  the  right  end  to  be  38°,  at  the 
left  end  26°.  At  this  moment,  all  Paramecia  are  in  the  left 
third  of  the  trough  (Fig.  72,  b).  If  now  the  hot  water  be 
passed  through  the  left  tube  only,  the  temperature  rises  at 
that  end  to  36°  or  38°,  falling  to  27°  or  28°  at  the  other,  and 


13-° 


26s 


385 


.'••  v~'.;^8| 
••  tttM 


10  Q 


25? 


FIG.  71. — Distribution  of  Paramecium  in  a  trough  of  water  with  variable  temperature 
at  the  ends.     (From  MENDELSSOHN,  '95.) 

the  Paramecia  swim  to  the  right  end.  Thus,  with  reference  to 
a  temperature  of  38°,  Paramecia  are  negatively  thermotactic. 

If,  now,  cold  water  be  passed  through  the  left  tube  so  that 
the  temperature  of  the  left  end  of  the  trough  falls  to  10°, 
while  the  right  end  is  at  25°,  the  Paramecia  migrate  to  the 
right  end.  Towards  a  temperature  of  25°  Paramecium  is  thus 
positively  thermotactic  (Fig.  72,  <?). 

Finally,  if  cold  water  be  passed  through  the  tube  at  one  end 
of  the  trough  and  hot  water  at  the  other,  the  organisms  will  be 
found  accumulated  in  the  middle  of  the  trough  where  the  tern- 


§  5]  THERMOTAXIS  261 

perature  ranges  from  24°  to  28°  C.  This  temperature  is  thus 
the  optimum  temperature  for  Paramecium,  the  temperature 
towards  which  it  tends  to  move  when  the  extremes  are  offered 
to  it.  Using  another  nomenclature,  we  may  say,  Paramecium 
is  attuned  to  a  temperature  of  24°  to  28°  C.,*  and  tends  to  keep 
in  the  temperature  to  which  it  is  attuned. 

Similar  results  have  been  obtained  by  DE  WILDEMANN  ('94) 
from  Euglense  which  were  kept  in  damp  sand  and  in  the  dark, 
in  a  horizontal  test-tube  warmed  at  one  end.  Under  these 
conditions  they  migrated  towards  the  temperature  of  30°  rather 
than  that  of  15  to  22°. 

Finally,  we  may  consider  thermotaxis  as  it  is  revealed  in  the 
higher  animals.  LOEB  ('90,  p.  43)  enclosed  the  larvae  of  the 
bombycid  moth  Porthesia  in  an  opaque  box,  one  end  of  which 
was  next  the  stove.  The  animals  moved  to  the  warmer  end  of 
the  box.  The  migration  differed,  however,  from  migrations 
with  reference  to  light  in  that  the  body  was  not  definitely 
oriented  with  reference  to  the  source  of  heat,  but  the  larvae 
wandered  thither.  Similarly  some  ants  (Formica  sanguinea) 
are  thermotactic  according  to  WASMANN  ('91,  p.  22);  and  the 
cockroach  (GRABER,  '87,  p.  254)  moves  towards  that  tempera- 
ture which  is  more  nearly  normal  for  it.  GRABER  ('83,  p.  230) 
has  likeAvise  shown  that  the  salamander  Triton  is  similarly 
responsive.  Thus  some  Metazoa  as  well  as  Protista  are  clearly 
thermotactic. 

Looking  now  for  the  cause  of  thermotaxis,  we  see  at  the  out- 
set that  it  is  necessary  to  distinguish  between  two  possibilities  : 
a  movement  towards  a  greater  or  less  intensity  of  heat,  and  a 
movement  with  reference  to  the  direction  of  the  heat  rays  in 
radiant  heat.  Now  we  have  seen  in  earlier  chapters,  in  con- 
sidering the  action  of  gravity,  the  electric  current,  and  light, 
that  these  agents  determine  the  direction  of  locomotion  by 
determining  the  orientation  of  the  axis  of  the  body;  and  since 
radiant  heat  passes  in  lines,  it  might  be  possible  to  have  a 
similar  effect  here.  But  there  is  no  evidence  that  radiant 
heat  acts  here.  In  the  case  of  the  Myxomycete,  it  is  clear  that 

*  Adequate  control  experiments  with  dead  Paramecia  and  fine  suspended 
particles  demonstrated  that  the  movement  was  not  purely  passive  ;  i.e.  due  to 
currents  in  the  water. 


262  HEAT  AND   PKOTOPLASM  [Cn.  VIII 

a  difference  in  the  temperature  of  the  two  ends  is  sufficient 
to  determine  direction  of  locomotion.  Iii  the  case  of  Para- 
mecium,  it  is  improbable  that  radiant  heat  acted,  since  this 
passes  with  difficulty  through  water.  Finally,  in  the  case  of 
the  insects  enclosed  in  a  box  there  is  evidence  of  no  axis  ori- 
entation, and  in  the  case  of  VERWORN'S  experiments  with  the 
Amoeba  the  action  of  direction  is  clearly  shut  out.  We  must 
therefore  conclude  that  direction  of  locomotion  in  thermotaxis 
is  not  usually,  if  ever,  determined  by  direction  of  heat  rays. 

Since  it  is  not  direction  of  heat  rays,  it  is  probably  difference 
of  intensity  of  the  agent  at  the  two  poles  of  the  organism 
which  is  the  determining  factor.  This  is  clearly  so  in  the  case 
of  the  Myxomycete  and  Amoeba.  In  the  case  of  insects  also,  it 
is  clear  that  one  part  of  the  body  being  appreciably  nearer  the 
source  of  heat  would  be  appreciably  warmer  than  the  other, 
and  this  difference  in  temperature  might  serve  as  an  indication 
to  the  organism  of  the  direction  of  the  source  of  heat.  But 
when  we  come  to  consider  MENDELSSOHN'S  experiments  on 
Paramecium,  we  pause  to  think  of  the  organism  being  so 
sensitive  as  to  be  affected  differently  at  the  two  poles  by  so 
slight  a  difference  of  intensity  as  these  poles  must  experience. 
MENDELSSOHN  has  found  that  the  least  difference  of  intensity 
at  the  ends  of  his  10  cm.  long  trough  which  will  call  forth  a 
thermotactic  response  is  3°  C.  The  length  of  a  Paramecium 
is  about  0.2  to  0.25  mm.,  which  corresponds  to  a  difference 
of  0.01°  C.  of  temperature  at  its  two  poles.  This  is  the  minimal 
temperature-difference  which  acts  as  a  stimulus  to  Paramecium 
and  calls  forth  a  thermotactic  response.  Although  this  differ- 
ence is  small,  we  must,  with  MENDELSSOHN,  in  the  absence  of 
opposing  data,  consider  it  the  determining  factor  in  thermo- 
taxis, and  conclude  that,  in  general,  the  thermotactic  response 
is  a  response  to  differences  in  the  intensity  of  heat  to  which 
the  two  poles  of  the  body  are  subjected. 

Let  us  now  sum  up  the  results  of  our  study  of  the  effect  of 
heat  on  protoplasm.  The  rates  of  the  metabolic  processes  and 
of  protoplasmic  movements  are  controlled  by  temperature,  since 
they  diminish  from  the  optimum  slowly  towards  the  minimum 
and  rapidly  towards  the  maximum.  At  these  points  movement 
and  irritability  cease  as  a  result  of  excessive  stimulation,  and 


NOTES   TO   TABLE  XXI  263 

either  the  beginning  of  coagulation  (maximum)  or  the  cessa- 
tion of  chemical  change  (minimum),  appears.  Finally,  death 
takes  place  at  the  ultramaximum  through  coagulation  of  the 
proteids,  while  it  may  occur  beyond  the  minimum  also,  if  the 
protoplasm  contains  much  water.  The  optimum  temperature 
is  unlike  in  the  different  species,  and  certain  individuals  even 
may  gain  a  very  high  or  low  optimum  (lying  even  beyond  the 
normal  extremes)  through  the  process  of  gradual  acclimatiza- 
tion. The  acclimatization  seems  to  be  due  to  the  direct  action 
of  the  varying  environment  upon  the  constitution  of  protoplasm. 
Finally,  many  simple  organisms  (probably  all  protoplasm)  re- 
spond to  heat  by  a  locomotion  which  is  adapted  to  keep  them 
at  the  temperature  to  which  they  are  attuned.  The  movement 
seems  to  be  determined  by  the  difference  in  intensity  of  heat  at 
the  different  parts  of  the  body.  This  whole  chapter  reveals 
protoplasm  as  a  substance  whose  integrity  is  limited  by  chemico- 
physical  conditions.  Within  those  limits,  however,  it  is  highly 
sensitive  to  changes  in  temperature,  becoming  so  altered  by  an 
untoward  temperature  as  not  to  be  injured  by  it,  or  migrating, 
if  possible,  so  as  to  keep  in  the  temperature  to  which  it  is 
already  attuned.  In  a  word,  protoplasm  shows  itself  to  be  a 
highly  irritable,  automatically  adjustable  substance. 


NOTES  TO  TABLE  XXI  (p.  250) 

1.  The  Chrob'coccus  was  found  in  some  of  the  fronds  of  Nostocs  from  Owen's 
Valley  (see  No.  3);  but  it  is  not  stated  whether  they  were  in  those  Nostocs 
which  were  derived  from  the  hottest  springs. 

2.  No  details  are  given  by  BREWER  concerning  the  method  of  determining 
temperature.     "  In  these  warm  mineral  waters  low  forms  of  vegetation  occur. 
The  temperatures  were  carefully  observed  in  many  cases.     The  highest  tem- 
perature noted,  in  which  the  plants  were  growing,  was  93°  C.  (about  200°  F.). 
But  they  were  most  abundant  in  waters  of  the  temperature  52°  to  60°  (125°  to 
140° F.).     In  the  hotter  springs  the  plants  appeared  to  be  of  the  simplest  kind, 
apparently,  simple  cells  of  a  bright  green  color ;  but  they  were  examined  only 
with  a  pocket  lens.     In  the  water  below,  about  60°  to  65°  C.,  filamentous  Con- 
fervas formed  considerable  masses  of  a  very  bright  green  color."     In  a  letter  to 
WYMAN,  however,  BREWER  says,  concerning  the  same  locality  and  determina- 
tions: "The  temperatures  given  here  were  carefully  observed  with  a  standard 
Centigrade  thermometer,  with  a  naked  elongated  bulb,"  and  "at  the  higher 
temperature  [93°  C.]  they  [the  vegetable  forms]  were  not  abundant  and  existed 
as  grains  like  Nostoc  or  Protococcus,  intensely  green  and  rather  dark." 


264  HEAT   AND   PROTOPLASM  [Cn.  V1I1 

3.  The  temperature  determinations,  like  the  organisms,  came  from  a  Mrs. 
PARTZ,  who  is  vouched  for  as  reliable.     No  details  concerning  the  method  of 
obtaining  temperatures  are,  however,  given.     The  springs  form  a  basin  from 
which  flows  a  creek.     "In  the  basin,"  says  Mrs.  PARTZ,  "are  produced  the 
first  forms  [Nostoc]  partly  at  a  temperature  of  124°  to  135°  Fahr.     Gradually 
in  the  creek,  and  to  a  distance  of  100  yards  from  the  spring,  are  developed,  at  a 
temperature  of  110°-120°Fahr.,  the  algae,"  etc. 

4.  Not  seen  by  me. 

5.  COHN  states  :  "  Thermometerbeobachtungen  zeigten  in  verschiedener  Tem- 
peratur  des  Wassers  verschiedene,  schon  durch  die  Farbe  erkennbare  Arten  ; 
zwischen  43°  und  35°  R.,  die  hellgrune  Leptothrix,  zwischen  35°  und  25°  die 
Oscillarien,  Mastichocladen,  etc.,  gesellt  mit  Raderthieren,  Infusorien  und  Was- 
seralchen  ;  in  noch  abkiihlterem  Wasser  die  f arblose  Hygrocrocis  nivea  ;  Was- 
ser  liber  44°  enthalt  keine  lebenden  Organismen.     Ganz  dasselbe  fand  AGARDH 
1827." 

6.  No  statement  as  to  the  method  of  determining  temperature.     The  meas- 
urements were  made  in  the  outlet  to  a  hot  spring.     In  this  outlet  Hypeothryx 
laminosa  flourished  at  68°  and  occurred  at  even  a  higher  temperature. 

7.  This  account  also  leaves  something  to  be  desired  as  to  defmiteness : 
"Small  springs  rise  at  intervals  of  10  to  20  feet  along  a  distance  of  30  to  40 
rods.    Their  waters  unite  and  form  a  little  stream  that  empties  into  a  brook  a 
short  distance  below.  ...     A  dense  mass  of  beautiful  green  confervae  grew 
about  the  bottom  and  sides  of  the  channel,  and  floated  in  rich  waving  masses  in 
the  hot  water.     In  the  immediate  vicinity  of  the  springs,  however,  no  vegetable 
growth  appears.  .  .  .    The  temperature  of  the  hot  stream,  below  all  the  springs, 
was  found  to  be  130°." 

8.  GERVAIS'  account  is  detailed,  but  the  method  employed  in  determining 
temperature  is  not  given.     The  principal  sections  of  interest  are  as  follows: 
"  Nous  avons  dit  que  1'eau  au  moment  ou  elle  s'e"chappe  des  sources  avait  donne" 
a  notre  thermometre  -f  95°  cent."     [It  cooks  eggs,  meat,  beans,  etc.]     "  II  est 
inutile  de  dire  qu'on  ne  trouve  en  cet  endroit  aucun  animal  ne  aucun  ve"ge"tal 
aquatique  vivant.      Cependant  on  voit  courir  sur  les  cones  d'ou  jaillit  1'eau 
bouillante,  et  en  des  points  ou  le  pied  e"prouve,  meme  a  travers  la  chaussure,  un 
sentiment  de  vive  chaleur,  de  petites  Araigne"es  qui  m'ont  paru  etre  du  genre 
Lycose.    Quelques-unes  s'aventurent  meme  et  cela  sans  inconvenient  a  travers  la 
surface  des  petits  crateres  remplis  d'eau  chaude  que  presentent  les  c6nes  dont  il 
s'agit.     Dans  la  substance  calcaire  ggalement  fort  chaude  d'un  de  ces  cones  que 
nous  percions  a  coups  de  pioche  pour  en  faire  sortir  1'eau  bouillante  par  le  flanc, 
nous  avons  trouve"  plusieurs  exemplaires  vivants  d'un  petit  Cole"optere  de  le  fa- 
mille  des  Hydrophiles,  V  Hydrobius  orbicularis,  qui  y  avaient  fixe"  leur  demeure. 

"  L'eau  a  +95°  qui  sort  de  diffe"rents  points  d'Hammam-Meskhputin  perd  assez 
rapidement  cette  temperature  e"leve"e.  Elle  n'a  de"ja  plus  que  57°  dans  les  vas- 
ques  du  second  tiers  de  la  cascade,  dans  lesquelles  on  commence  a  trouver  des 
productions  cryptogamiques.  Celles-ci  sont  en  partie  couvertes  d'un  enduit 
i'errugineux  assez  e"pais." 

9.  Plants  found  in  samples  of  water  from  Taupo,   "growing  in  water  the 
temperature  of  which  varied  from  105°  F.  to  131°."     Two  individuals  are  given 
as  occurring  at  "temp.  136°";  two  at  "temp.  116°." 

10.  See  note  2. 


NOTES   TO   TABLE   XXI  265 

11.  The  reference  reads:  "Not  only  confervas  and  other  vegetables  grow  in 
and  about  the  hottest  springs,  but  great  numbers  of  little  insects  are  constantly 
sporting  about  the  bottom  and  sides."     The  temperature  of  the  various  springs 
runs  from  92°  to  151°  F. 

12.  DANA  says:  "A  species  of  feathery  vegetation  occurs  also  upon  them 
[the  stones  of  the  brook],  bordering  the  streamlets  where  the  temperature  is 
160° F.,  and  presenting  various  shades  of  green  and  white." 

13.  Data  concerning  temperature  incomplete.     "Confervse  abound  in  the 
warm  stream  from  the  springs,  and  two  species,  one  ochreous  brown,  and  the 
other  green,  occur  on  the  margins  of  the  tanks  themselves,  and  in  the  hottest 
water ;  the  brown  is  the  best  salamander,  and  forms  a  belt  in  deeper  water  than 
the  green  ;  both  appear  in  luxuriant  strata,  wherever  the  temperature  is  cooled 
down  to  168°,  and  as  low  as  90°." 

14.  This  seems  a  carefully  observed  case.     Hot  water  flowed  from  the  clefts 
of  the  rock.     "Die  flache  und  schroffe  Felswand  worauf  das  heisse  Wasser 
rieselnd  und  tropfend  herabfloss  war  mit  2  fingerdicken  hell  und  dunkelgriinen 
Oder  auch  gelben,  rothlichen  und  braunen  Filzen  iiberdeckt.     In  diese  Filze  an 
den  Spalten  eiugesenkt  zeigte  das  Thermometer  65  bis  68°  R. ,  entf ernter  von 
der  Spalte  schnell  abnehmend  weniger.    Die  organischen  Filze  waren  so  heiss, 
dass  sie  mit  den  Fingern  nicht  fassbar  waren."     Examined  microscopically,  the 
mass  was  found  to  consist  partly  of  dead,  partly  of  living  "  Eunotia  forms" 
overgrown  with  Oscillaria.    A  similar  condition  was  found  also  "  in  der  Schlecht 
der  Acqua  della  Rita  bei  eine  Temperatur  von  59°  R.  .  .  .  Ich  untersuchte  in  Serra- 
valle  aufgefangenes  Wasser  von  65°  R.    Warme,  welches  ich  in  ein  Glas  lauf en 
liess,  wahrend  ich  die  felzige  Masse  driickte.    Es  war  sehr  voll  von  vielartigen 
lebenden   kleinen  Thieren.     Darunter  war  4  Arten  munter  bewegter  Rader- 
thiere,  namlich   Diglena    Catellus,    Conurus  uncinatus,  die  Abanderung  des 
Brachionus  Pola  mit  kleinen  Stirnzahnen  am  Schilde,  auch  Philodina  erythro- 
phthalma,  ausgebildete  Eier  im  Innern  fiihrend.     Von  Polygastern  fanden  sich 
in  frischer  Lebensthatigkeit  eine  noch  unbekannte  eigenthiimliche,  kleine  Xas- 
sula,  Formen  von  Enchelys  und  Amphileptus  von  weniger  sich  auszeichender 
Gestaltung.     Besonders  auffallend  war  die  lebende  Eunotia  Sancta  Antonii  der 
Capverdischer  Inseln,  deren  Lebenszustand  und  Lebensbedingungen  hierdurch 
zum  erstenmale  bekannt  werden."     Despite  the  evident  care  taken  to  obtain 
accurate  results,  EHRENBERG'S  observations  have  not  been  confirmed  by  HOPPE- 
SEYLER  ('75,  pp.  119,  120),  who  examined  Ischia,  but  found  no  algse  living  at  a 
temperature  much  above  60°. 

15.  The  entire  reference  is  this  :  "  M.  FLOURENS  met  sous  les  yeux  de  1'Aca- 
de"mie  des  confei'ves  recueillies  en  Islande  par  M.  DESCLOIZE  AUX,  qui  les  a  trouve"es 
ve"ge"tant  dans  la  source  thermale  de  Grof,  a  une  temperature  de  98  degre"s"  [of 
course,  C.].     HOOKER  ('13,  p.  160)  is  often  quoted  as  having  obtained  vegeta- 
tion in  Icelandic  hot  springs.     Unfortunately,  he  gives  no  temperature  deter- 
minations.    He  says :  "Close  to  the  edge  of  many  of  the  hot  springs  [vicinity 
of  the  Great  Geyser],  and  within  a  few  inches  of  the  boiling  water,  in  places 
that  are,  consequently,  always  exposed  to  a  considerable  degree  of  heat,  arising 
both  from  the  water  itself  and  the  steam,  I  found  Conferva  limosa  Dillw.  in 
abundance."    Again,  "  In  water,  also,  of  a  very  great  degree  of  heat,  were,  both 
abundant  and  luxurious,  Conferva  flavescens  of  Roth  and  a  new  species  allied 
to  C.  rivularis." 


266  HEAT   AND  PROTOPLASM  [Cn.  VIII 

16.  The  temperatures  were  not  taken  on  the  spot.     MOSELEY  says :  "  The 
water  from  which  the  Algae  were  gathered  was  in  the  pools  from  which  the 
Chroococcus  was  collected  as  far  as  I  can  now  [i.e.  many  months  after  (?)]  judge 
after  testing  water  of  successive  temperatures  with  my  finger,  about  149°- 
158°  F.     The  water  of  the  sulphur-springs,  in  the  area  splashed  by  which  the 
Oscillatoria  are  found,  is  quite  scalding  to  the  hand,  and  probably  between  176° 
to  194°  F." 

17.  The  reference  reads :  "Dans  celle  [source  chaude]  de  Saint  Pierre,  dont 
la  temperature  varie  de  33  a  35  degre"s,  les  Physa  acuta,  Drap.  sont  en  nombre 
si  considerable  qu'elles  forment  un  veritable  fond  mouvant  dans  les  canaux." 
These  hot  water  molluscs,  as  experiment  showed,  were  killed  at  about  43°, 
while  Physa  from  ordinary  sources  die  at  once  at  35°.     They  perished  after  a 
few  hours  at  5°  or  6°. 

18.  Merely  the  note:  "On  en  [living  mollusca]  trouve  aussi  dans  des  eaux 
thermales :  par  exemple  le  turbo  thermalis,  espece  de  paludine  sans  doute,  vit 
dans  celles  d'Abano,  dont  la  temperature  est  de  40°  R." 

19.  The  statement  is  not  critical:  "Their  heat  [hot  springs]  is  too  great 
for  the  hand  to  bear;   the  highest  temperature  is  about  150°."     "In  the  hot 
water  of  these  springs  a  green  plant  vegetated,  which  seemed  to  be  a  species  of 
conferva  growing  in  such  situations :  probably  the  fontenalis.    But  what  is  more 
remarkable,  a  bivalve  testaceous  animal  adhered  to  the  plant,  and  lived  in  such 
a  high  temperature  too." 

20.  See  note  5. 

21.  "  J'ai  mesure"  plusieurs  fois  &  en  diverses  saisons,  la  chaleur  de  ces  eaux, 
&  je  1'ai  toujours  trouve'e  a  tres-peu  pres  la  meme  ;  savoir,  de  35  degr^s  dans 
celle  du  soufre,  &  de  36^  ou  36.7  [R.  from  context]  dans  celle  de  St.  Paul. 
Malgr6  la  chaleur  de  ces  eaux,  on  trouve  des  animaux  vivans  dans  les  bassins 
qui  les  regoivent ;  j'y  ai  reconnu  des  rotife"res,  des  anguilles  &  d'autre  animaux 
des  infusions.     J'y  ai  meme    de"couvert  en  1790,  deux  nouvelles   especes  de 
tremelles  douses  d'un  inouveinent  spontane*." 

22.  See  note  No.  14. 

23.  Many  individuals  collected  by  R.  BLANCHARD  "dans  les  eaux  de  thermes 
du  Hamman-Meskhoutine,  pres  Guelma,  dans  les  premiers  jours  d'avril ;  Peau 
des  thermes,  au  point  de  la  re'colte,  a  une  temperature  de  45°  et  de  50.5°  C. 
Les  Cypris  formaient  une  sorte  de  zone  continue,  de  couleur  chocolat,  sur  le 
bord  de  Peau." 

24.  Found  "  in  a  hot  spring,  temperature  157°  F.,  attached  to  the  rock  by 
the  long  end  at  about  an  angle  of  45°  and  continually  moving.  .  .  .     The  rocks 
were  covered  with  them." 

25.  The  note  in  "Insect  Life "  is  abstracted  from  a  longer  article  by  BRUNER 
in  the  newspaper  called  the  Lincoln  (Nebraska)  "Evening  Call,"  for  April  6, 
1895.     The  article,  through  the  kindness  of  Professor  H.  B.  WARD  of  the  Uni- 
versity of  Nebraska,  I  have  now  before  me.     The  larvae  were  sent  to  Professor 
BRUNER  by  JOHN  C.  HAMM,  of  Evanston,  Wyoming,  upon  whom  this  statement 
of  the  conditions  of  life  of  the  organisms  depends.     The  larvae  were  found  in  a 
cup-shaped  depression  in  the  top  of  a  small  isolated  cone  about  20  inches  high, 
situated  about  a  few  feet  from  a  large  sulphur  mound  or  "dune,"  under  which 
one  could  hear  the  rumbling  of  boiling  water.     Through  apertures  in  the  bottom 
the  almost  boiling  water  came  up  into  the  cup  and  ran  over  the  edge  of  the  pot. 


LITERATURE  267 

The  larvae  were  actively  moving.  Mr.  HAMM  writes  to  Mr.  BRUNER:  "I  did 
not  have  a  thermometer  with  which  to  take  the  temperature,  but  .  .  .  the  water 
was  so  hot  when  I  saw  them  that  I  could  not  hold  my  hand  in  it.  My  best 
judgment  is  and  was  at  the  time  that  the  water  was  not  more  than  twenty  or 
thirty  degrees  [Fahr.,  of  course]  below  the  boiling  point." 

26.  "  A  water  beetle  abounded  in  water  at  112°  "  [F.]. 

27.  Too  hot  for  the  hand  to  bear  more  than  a  moment  or  two. 

28.  The  reference  is  to  a  discussion  of  a  paper  by  BERT.     "  M.  PAUL  BERT  a 
vu  des  barbellons  dans  de  1'eau  a  34°  C." 

29.  "  Mon  ami  Mr.  COCCHI,"  says  SPALLAXZANI,  "  raconte  que  les  Grenouilles 
ne  souffrent  point  dans  les  bains  de  Pise,  quoiqu'elles  soient  exposes  a  une 
chaleur  mdique"e  par  le  111°  du  Thermometre  de  FAHRENHEIT  qui  correspond  au 
37°  du  Thermometre  de  REAUMUR  [!  sic]." 


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268  HEAT   AND   PROTOPLASM  [Cn.  VIII 

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270  HEAT   AND  PROTOPLASM  [Cn.  VIII 

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272  HEAT  AND  PROTOPLASM  [Cn.  VIII 

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CHAPTER   IX 

GENERAL  CONSIDERATIONS  ON  THE  EFFECTS  OF  CHEM- 
ICAL AND  PHYSICAL  AGENTS  UPON  PROTOPLASM 

IN  the  present  chapter  it  is  proposed  to  consider  certain 
general  matters  upon  which  the  facts  given  in  this  First  Part 
throw  light :  namely,  (I)  the  structure  and  composition  of 
protoplasm ;  (II)  the  limiting  conditions  of  metabolism  ; 
(III)  the  dependence  of  protoplasmic  movement  upon  metabo- 
lism and  external  stimuli ;  and  (IV)  the  determination  of  the 
direction  of  locomotion. 
/ 

§  1.   CONCLUSIONS  ON  THE  STRUCTURE  AND  COMPOSITION 
OF  PROTOPLASM 

The  question  of  the  structure  of  protoplasm  is  preeminently 
a  histological  one.  Microscopical  study  ^nust  eventually  be  re- 
lied upon  to  settle  it.  However,  the  results  of  experimental  work 
seem  to  favor,  as  we  have  already  pointed  out  (p.  70),  BUTSCHLI'S 
view  of  a  honeycomb,  or  foam  structure,  of  protoplasm. 

The  problem  of  the  constitution  of  protoplasm  is,  on  the  other 
hand,  preeminently  a  chemical  one,  and  it  must  be  solved  by 
experimental  methods.  Our  results  can  lead  us  to  certain 
qualitative  statements  on  this  matter. 

The  chemical  composition  of  protoplasm  is  immensely  com- 
plex. Just  as  the  geologist  is  forced  by  the  facts  to  assume  a 
vast,  but  not  infinite,  time  for  earth  building,  so  the  biologist 
has  to  recognize  an  almost  unlimited  complexity  in  the  consti- 
tution of  protoplasm. 

The  evidence  that  protoplasm  is  so  complex  is  gained  partly 
from  the  results  of  micro-chemistry.  Many  staining  fluids  act 
upon  only  a  small  part  of  the  protoplasm  of  a  single  cell,  so 
that  a  mixture  of  stains  may  be  used,  each  component  of  which 

274 


§  2]  LIMITING  CONDITIONS  OF  METABOLISM  275 

attacks  a  different  constituent  of  the  protoplasm.  In  this  way 
the  dissimilar  substances  in  protoplasm  are  made  strikingly 
apparent.  Not  only  does  the  protoplasm  of  one  cell  show  this 
differentiation,  but  that  of  different  cells  of  the  body  stains  very 
diversely.  Another  line  of  evidence  for  the  complexity  of  pro- 
toplasm is  gained  from  the  study  of  the  effect  of  poisons.  We 
have  seen  that  the  same  poisonous  substance  acts  very  differently 
upon  allied  species  of  organisms  (e.g.  of  bacteria)  and  upon  the 
various  organs  of  the  body,  —  a  fact  which  in  many  cases  can 
only  be  accounted  for  on  the  ground  of  dissimilar  composition. 
Again,  most  protoplasm  must  contain  substances  which  are 
acted  upon  specifically  by  the  different  agents ;  for  instance, 
certain  highly  explosive  compounds  which  are  set  off  by  contact, 
certain  others  which  are  disturbed  by  light,  and  still  others 
which  are  especially  changed  by  heat.  Each  compound,  again, 
must  form  an  inconsiderable  part  of  the  whole,  for  (if  the 
action  be  not  too  intense  or  prolonged)  the  "stimulus"  of  the 
agent  results  in  no  disturbance  of  the  activities  in  general. 
Likewise,  the  facts  of  acclimatization,  according  to  which,  ap- 
parently, certain  substances  in  the  protoplasm  may  be  destroyed 
without  other  important  change  in  activities,  give  additional 
insight  into  protoplasmic  complexity.  Finally,  the  same  agent 
acts  in  varying  degre"e  on  closely  related  protoplasm,  and  this 
indicates  that,  even  when  the  general  composition  is  the  same, 
the  proportions  of  the  different  substances  vary.  From  the 
facts  of  protoplasmic  staining  and  of  the  varied  effects  of  poi- 
sons, from  the  diverse  effects  of  other  stimulating  agents,  and 
from  the  facts  of  acclimatization  of  organisms,  we  conclude 
that  in  dealing  with  protoplasm  we  are  not  always  dealing  with 
the  same  thing,  but,  on  the  contrary,  with  very  diverse  combi- 
nations, which  have  this  in  common,  that  they  exhibit  life. 

§  2.   THE  LIMITING  CONDITIONS  OF  METABOLISM 

Metabolism  is  life.  To  know  the  limits  within  which  it  can 
occur  is  to  know  the  vital  limits.  It  is  impossible  to  define 
these  limits  closely,  however,  for,  at  either  extreme,  metabolism 
graduates  insensibly  into  inaction.  It  will  be  necessary,  conse- 
quently, to  place  our  limits  very  far  out. 


276  GENERAL   CONSIDERATIONS  [Cn.  IX 

The  limiting  conditions  at  which  inaction  occurs  are  of  two 
sorts.  These  may  be  termed  respectively  structural  and  dynami- 
cal. These  two  sorts  of  limiting  conditions  may  be  illustrated 
by  comparing  the  protoplasmic  mass  to  a  factory,  with  many 
-  boilers  and  engines,  much  shafting  and  belting,  and  countless 
machines  doing  the  most  varied  work.  The  amount  of  energy 
developed  in  the  boilers  and  the  efficiency  of  the  engines  and 
machines  varies  with  certain  conditions,  such  as  the  amount  of 
heat  applied  to  the  former,  and  the  friction  and  waste  in  the 
latter.  The  limiting  mechanical  conditions  are  reached  when 
the  boiler  is  rent  by  the  steam  pressure,  a  break-down  is  caused 
by  friction,  or  a  part  rusts  through  and  crumbles  away.  The 
limiting  dynamical  conditions  are  reached  when  the  heat  no 
longer  suffices  to  form  steam  in  the  boiler,  or  the  power  is 
insufficient  to  run  the  machines.  In  either  case,  at  the  structu- 
ral, or  at  the  dynamical  limit,  work  ceases.  It  may  be  the 
work  of  a  small  part  of  the  factory,  so  that  the  cessation  is 
hardly  noticed ;  or  it  may  involve  all  the  machines,  producing 
complete  cessation  of  activity. 

To  return  to  the  protoplasm  :  the  structural  limiting  condi- 
tions are  of  two  main  sorts,  —  mechanical  and  chemical.  The 
mechanical  limiting  conditions  are  those  in  which  the  gross 
structure  becomes  broken  down,  while  the  chemical  limiting 
conditions  are  those  in  which  the  composition  becomes  changed. 
To  the  mechanical  group  belongs  the  breaking  down  of  the 
plasma  films,  either  by  drawing  out  the  water  of  the  protoplasm 
(by  osmosis  or  by  drying)  or  by  the  expansion  due  to  the 
freezing  of  the  chylema.  To  the  chemical  group  belong,  for 
example,  the  reactions  upon  protoplasm  of  the  halogen  salts 
of  the  heavy  metals,  and  of  complex  nitrogenous  organic  com- 
pounds in  whose  molecules  hydrogen  is  unstably  joined  to 
nitrogen,  also  the  coagulation  of  the  plasma  by  high  tempera- 
tures and  the  destruction  of  molecules  by  contact,  by  the 
electric  current,  or  by  light.  The  dynamical  limiting  condi- 
tions, on  the  other  hand,  are  the  absence  of  oxygen  or  other 
food-stuffs,  the  absence  of  the  water  necessary  to  the  solution 
and  circulation  of  the  food,  absence  of  light,  in  the  case  of 
chlorophyllaceous  organisms,  and  a  temperature  much  below 
0°C.  Thus,  the  conditions  essential  to  metabolism  are  the 


§  3]  PROTOPLASMIC   MOVEMENT  277 

absence  of  causes  mechanically  rupturing  the  machine,  the 
absence  of  agents  of  such  intense  activity  as  to  change  pro- 
foundly its  molecular  constitution,  and  the  presence  of  those 
agents  —  food,  heat,  light,  and  water  —  which  supply  or  dis- 
tribute the  energy  of  metabolism. 

Given  protoplasm  under  these  conditions,  and  normal  me- 
tabolism must  occur ;  without  them,  there  is  no  metabolism. 
Vary  the  dynamical  conditions  quantitatively,  and  a  quantita- 
tive variation  in  metabolism  will  ensue.  Approach  a  struct- 
ural limiting  condition,  and  metabolism  begins  to  cease. 
This  conclusion,  important  for  experimental  morphology,  is 
now  reached  :  A  vital  phenomenon  occurring  in  a  given  proto- 
plasmic mass  can  be  reproduced  only  when  the  dynamical  condi- 
tions are  reproduced,  and  the  structural  limiting  conditions  are 
in  no  wise  closely  approached. 

§  3.     THE    DEPENDENCE    OF    PROTOPLASMIC    MOVEMENT 
UPON  METABOLISM  AND  UPON  EXTERNAL  STIMULI 

I  do  not  propose  to  enter  the  debated  ground  of  the  cause 
of  protoplasmic  motion;  but  shall  merely  summarize  the  re- 
sults of  our  studies  on  this  subject.  First,  protoplasmic 
movement  is  closely  related  to  metabolism  and  is  probably 
dependent  upon  it.  This  is  indicated  by  the  fact  that  ces- 
sation of  movement  always  occurs  before  the  vital  limit  is 
reached.  Rigor  always  precedes  death.  A  second  series  of 
facts  indicating  the  same  thing  is  found  in  the  closeness 
with  which  the  optimum  for  metabolism  agrees  with  the 
optimum  for  movement.  Thus  at  about  35°  C.  both  the 
metabolic  processes  and  the  movements  of  protoplasm  find 
their  optimum.  These  two  results,  then,  that  movement  is 
impossible  in  dead  protoplasm  even  when  its  structure  is 
seemingly  unaltered,  and  the  close  approximation  of  the 
optimum  points  for  metabolism  and  for  movement,  are  the 
best  justification  for  the  belief  that  movement  is  dependent 
upon  metabolism. 

But  are  the  conditions  essential  to  metabolism  the  only  con- 
ditions necessary  for  movement  ?  In  other  words,  will  move- 
ment always  accompany  metabolism,  or  are  external  stimuli 


278  GENERAL   CONSIDERATIONS  [Cii.  IX 

essential  to  its  production?  There  is  in  biology  no  question 
more  important  than  this,  and  the  answer  is  not  so  certain  as 
it  ought  to  be.  The  fact  that  rigor  occurs  at  a  point  at  which 
recovery  of  movement  is  still  possible  is  not  sufficient  evidence 
that  metabolism  has  not  ceased  with  the  motion  ;  for  I  think  it 
has  not  been  shown  that  with  rigor  "  latent  life  "  does  not  come 
in.  On  the  other  hand,  the  fact  that  some  bacteria  are  motion- 
less in  the  absence  of  light  (which  can  hardly  be  essential  to 
metabolism)  would  seem  to  indicate  that  conditions  other  than 
those  of  metabolism  are  necessary  to  movement.  This  single 
fact  cannot,  however,  lead  us  to  a  definite  answer,  and  our 
inquiry,  whether  or  not  "stimuli"  are  essential  to  protoplasmic 
movement,  must  still  be  regarded  as  unanswered. 

§  4.     THE  DETERMINATION  OF  THE  DIRECTION  OF 
LOCOMOTION 

As  we  watch  an  animalcule  swimming  across  the  field  of  view, 
or  as  we  see  a  larger  organism  moving,  perhaps  in  a  broken 
line,  towards  any  point,  we  think  of  its  movements  as  controlled 
from  inside.  Yet  it  is  clear  that  if  an  organism  is  moving 
definitely  towards  a  point,  it  must  be  on  account  of  some  influ- 
ence emanating  from  that  point  and  falling  upon  the  organism. 
Without  external  directive  influences  of  some  sort  there  can  be 
110  directed  movements. 

This  conclusion  is  confirmed  by  experiment.  I  have  put  an 
amoeba  into  the  apparatus  already  described  (p.  186),  so  that 
the  chemical  conditions  of  its  environment  were  uniform  ;  con- 
tact and  temperature  were  also  similar  011  all  sides  ;  the  direc- 
tive action  of  gravity  was  annulled  and  all  light  was  cut  off. 
At  intervals  the  position  of  the  amoeba  was  platted  by  the  aid 
of  light  reflected  momentarily  from  below  the  stage  of  the 
microscope  and  by  means  of  a  camera.  Thus  the  path  of  the 
amoeba  was  traced.  A  typical  tracing  made  in  this  way  is 
reproduced  in  Fig".  72.  Compare  the  devious  path  made  under 
these  conditions  with  the  straight  path  taken  in  response  to 
light  (Fig.  53).  The  curious  spiral  twists  and  the  turning  of 
the  line  upon  itself  are  characteristic  of  all  the  tracings  which 
I  have  made  under  these  conditions.  Important  also  is  the 


§4] 


DIRECTION  OF  LOCOMOTION 


279 


10:58 


11:02 


:20 


:56 


:52 


FIG.  72. —  Camera  drawing,  showing  the  successive  positions  assumed  by  Amosba 
proteus  when  acted  upon  by  external  agents  uniformly  in  all  directions.  Mag- 
nified 16  diams. 


FIG.  73.  —  Tracks  made  on  paper  by  larvae'  of  Musca  caesar  moving  in  the  dark  from 
a  central  spot  of  colored  fluid.  (From  POUCHET,  '72.  Revue  et  Mag.  de  Zool. 
(2)  XXIH.) 


280  GENERAL   CONSIDERATIONS  [Cn.  IX 

fact  that  whereas  the  amoeba  responding  to  light  is  constantly 
elongated  in  the  direction  of  the  infalling  ray,  the  amoeba 
which  is  not  stimulated  from  one  direction  exhibits,  most  of 
the  time,  a  stellate  appearance.  The  wandering  of  the  undi- 
rected organism  is  illustrated  again  in  the  experiment  of 
Pouchet  on  the  larvae  of  Musca  (Lucilia)  csesar,  kept  in  the 
dark  (Fig.  73  ;  compare  Fig.  74,  where  the  same  larvae  are 
migrating  under  the  directive  influence  of  light). 

From  these  experiments  we  make  the  deduction  that  external 
agents  play  a  role  of  the  utmost  importance  for  morphology,  — 
of  the  utmost  importance  because  by  them  alone  is  determined 
the  direction  of  migration  of  the  motile  cells  or  the  migrating 


FIG.  74.— Tracing  made  like  that  of  Fig.  73  by  fly  larvae,  when  the  light  falls  upon 
them  in  the  direction  of  the  arrow.  A,  the  first  direction  of  the  light;  J5,  the 
second  direction.  To  be  compared  with  the  undirected  movements  of  Fig.  73. 
(From  POUCHET,  '72.) 

protoplasm  of  whatever  sort  in  the  organism.  The  sense  of 
that  migration  depends  in  part  upon  the  internal  condition  of 
the  protoplasm.  The  mechanism  by  which  locomotion  is  effected 
—  that  is  wholly  internal.  The  mechanism  and  the  energy 
necessary  to  make  it  go  are  alone  impotent  to  determine  any 
adaptive  movement  or  any  other  predictable  result.  To  mech- 
anism and  energy  must  be  added  a  stimulus  external  to  the 
responding  protoplasm  in  order  that  an  adaptive  or  orderly 
result  should  occur.* 


*  There  are  several  other  important  matters  upon  which  the  results  of  this 
First  Part  throw  light,  such  as  the  Mechanics  of  Response  and  the  Origin  of 
Adaptation  in  Response.  Since  additional  facts  for  the  discussion  of  these 
topics  will  be  gained  from  the  succeeding  Parts,  that  discussion  will  be  deferred. 


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